Pulse was kind enough to compile a thread regarding flash drives as it seems people don't quite understand all the nitty gritty about them. And we're here to do what we do best - help you out!

Capacity
You get home with your shiny new 8GB flash drive, plug it in and notice that it only has 7.67GB of capacity. What gives? It's all math! There's 1024 bytes per kilobyte, 1024 kilobytes per megabyte, 1024 megabytes per gigabyte. 1GB isn't 1,000,000,000 bytes, it's 931,322,574 bytes. Don't worry, it's not just you and you're not being gypped.

It doesn't matter what capacity you buy but remember that you'll always pay more to be on the "bleeding edge". As of this writing, 32GB is the largest drive on the shelf, but it will cost you around the $130 mark to have that much storage in your pocket. A 16GB drive will set you back $50-70. 8GB and 4GB drives are in the $25-40 and $15-30 ranges respectively. If you're talking bang-for-your-buck averages:

$4.00/GB for a 32GB stick
$3.75/GB for a 16GB stick
$4.00/GB for a 8GB stick
$5.50/GB for a 4GB stick

You can see that they're close but your best bet is a 16GB stick - but remember that's the average. At the top end of the 16GB spectrum, you could pay $90 (which works out to $5.63/GB), but that won't necessarily net you the best drive.

Speed
Many manufacturers test their drives with one large file which skews the results since an operating system can handle one large file faster than many small files. There's also a difference between continuous (sequential) reading/writing and scattered random reading/writing. 

As DJs, we transfer multiple folders with files in the 3-15MB range (typical sizes for 320k MP3s). The good thing is a drive's speed won't play much part of the actual DJing process. Why is this? 

A 320k MP3 streams data at 320Kb per second (note the small b - that's for BITS). That's 40KB/s (note the large B - that's for BYTES and there's 8 bits per byte), far below the USB1.1 standard of 12MB/s.

The key for a high-speed drive is in the amount of time it takes you to load-up the drive with new music.

Extras
U3, ReadyBoost, SecureStore, etc... these are ALL UNNECESSARY! Encryption software is totally undesirable for DJ purposes and auto-encrypting drives are only going to be more expensive and give you the potential for problems. U3 drives are bad news because they create a virtual partition. Do away with it right away. Go here to get a U3 removal utility specifically designed for your brand of drive. The only good thing to say about ReadyBoost is those devices are typically a bit faster than the rest of the pack.

File Format
No matter what format your drive arrives in, FAT32 is your best bet because it will work with both Mac and PC machines. If it's a new drive, format the thing using a FULL FORMAT (not the "Quick" variety) and do it TWICE. This will help dodge problems down the road.

Housing
Metal, plastic, rubber, waterproof, impact-resistant, folding, no-LED, an LED you could use to land airplanes or blind assailants... there are endless choices as to the housing for the USB drive.

While it doesn't really matter what the memory itself is encased within, you should probably get something durable enough to withstand the rigors of DJ use. Let's face it, we're rough with the gear and no matter how hard we try, something's bound to break.

Having used several different types of drives, I would avoid anything with a retractable USB connector as well as smaller, flimsy housings.

Freebies
We all love freebies but the free flash drives handed out (by what seems like almost anyone these days) are typically garbage. They're meant to be cheap to keep costs low, they're not performance units. Use them for personal stuff, not for DJing (unless you give them out with your mix stored on it, but even then the recipient could just erase it without even listening!). Personally, I keep a couple around with various firmwares stored within for updating or re-flashing hardware while out and about. Perhaps a backup copy of your DJ software or even some PortableApps for working with your own programs and data on the road without your own computer!

Drive Reviews
As I said above, I've used plenty of flash drives so here's a quick review and benchmark of several flash drives I had kicking around.

 

A) Maxell generic promotional drive (512MB)
- Average Read Speed: 10MB/s (link to graph)
- Status indicator: Ugly green LED
- Retractable USB connector (bleh)

B) Generic promotional drive (Avery labels) (256MB)
- Average Read Speed: 4.8MB/s (link to graph)
- Status indicator: Tiny ugly green LED
- Flip-style cover - nice that it can't be lost but I don't like the pocket clip so much, plus it had a hideous Avery logo on it so I took a Sharpie to the whole thing.

C) Patriot XT (8GB)
- Average Read Speed: 28.6MB/s Fastest of the bunch in real-world testing too! (link to graph)
- Status indicator: Tiny inoffensive blue LED
- Awesome rubber housing but I was disappointed that the lanyard loop is only rubber and not rubberized metal connected to the drive itself. Rubber end-cap. 

>> UPDATE >> I have to point out that this unit has one serious flaw and that's the build itself. The rubber housing sits outside a plastic shell which encases the electronic components. If you should be as stupid as I am and accidentally pull the lanyard and the housing of the flash drive away from the computer while diving to answer the phone, you may end up doing what I did which is to tear the outer casing completely off the innards and breaking the USB connector from the circuitboard in the process. Yes, I wrecked this flash drive by accident and I'm not proud of it. Yes, it had data on it but I will be able to recover it by re-soldering the connections, but it will be retired immediately following that. It is with regret that I lower my opinion of this drive -- my current picks are the OCZ drives (all metal enclosure) and the Corsair Survivor.

D) SanDisk Cruzer Mini (512MB)
- Average Read Speed: 15.1MB/s (link to graph)
- Status indicator: Ugly green LED at the end of the unit
- Simple, came with 3 plastic end-caps so I can always replace it. 

E) OCZ Rally (512MB)
- Average Read Speed: 28.5MB/s (link to graph)
- Status indicator: Inoffensive blue LED at the end of the unit.
- Metal housing takes a beating (as mine has), a very solid unit. Metal end-cap.

F) OCZ Rally2 (4GB)
- Average Read Speed: 27.7MB/s (link to graph)
- Status indicator: A freaking LIGHTHOUSE-power orange LED at the end of the unit - I wish it weren't so bright.
- Metal housing looks as solid as my old Rally unit. Metal end-cap.

G) Pioneer generic promotional drive (1GB)
- Average Read Speed: 13.9MB/s (link to graph)
- Status Indicator: A little red LED which is hard to see on off-angles.
- Metal swivel cover and rubber housing is decent, loop isn't big enough for a key-ring though.

H) Lexar JumpDrive Firefly (4GB)
- Average Read Speed: 11.8MB/s (link to graph)
- Status Indicator: The entire end of the unit lights up blue, verges on annoying but not too bad.
- Plastic housing with a removable plastic cap. The lanyard loop is on the cap which I find a bit useless. It's a tiny little unit but the performance is lacking.

I) OCZ Roadster (1GB)
- Average Read Speed: 10.0MB/s (link to graph)
- Status Indicator: None
- This unit is so tiny that the entire drive is barely larger than the USB connector! It's the kind you NEED a lanyard on so you won't lose it. It's too bad the performance isn't as cool as the size of this minute drive.

J) SanDisk SD Card (1GB) in generic reader
- Average Read Speed: 6.4MB/s (link to graph)
- Status Indicator: Depends on the reader, mine has a little green LED
- I don't think this is really a great solution but I figured I'd test this out as someone would be bound to try it. As a standard SD card, it's not tremendous for speed but you can certainly get higher-end cards.

K) Corsair Survivor (16GB) [Not Pictured]
- Average Read Speed: 20.3MB/s (link to graph)
- Status Indicator: A little blue LED just below the threads for the cap.
- This unit is supposed to be one of the toughest on the market. When encased in its outer "armor", the drive is water resistant to 200M, drop-proof (I think that means it won't be affected by any impacts) and even carries a warranty which will last longer than the usefulness of the drive itself - 10 years. When the sleeve is over the drive, it's big and heavy, I won't deny that, but it also does really seem to be durable and rugged. I'd feel confident having my data on this drive provided the lid is on tight. The speed isn't too shabby so it was well worth the sale price.

Closing Comments

I'm sure others would appreciate your own reviews in addition to mine. If you want to benchmark your own drives and provide information and feedback similar to what I've done, you can download the benchmarking software here and post a reply!

<update 2008-12-23> I just found a FANTASTIC review by TestFreaks, it reviews 21 drives and shows them with much better speed comparison charts than my tests do. Check out the test results here.

<update 2009-05-14> I found another awesome drive comparison today and wanted to update this post to share it.ArsTechnica on the task of reviewing some seriously fast drives, a couple of which I mention in my test above!

<update 2011-06-20> I've purchased a Patriot Rage XT 32GB with quad-channel memory, and while I haven't done a speed test or graph as I had for the other drives above, it smokes the pants off the rest of the drives I have in terms of read/write speeds.  Get one.  Heck, if they're on sale, get two!