I have both units, and have used them for a while,
If your not a professional Dj, with a huge collection of CD's , then the XDJ Aero is for you,
It has much better stability, much more connectivity, Fully Supports Virtual Dj Pro, and if you have a laptop or macbook, you can drag and drop songs from your Rekordbox Collection to the Aero, it also supports most Tablets with Android, and the IPad/Ipod as well,
The XDJ R-1 has a more professional feel to it, so if you were an established Dj , the XDJ R1 would probably be your choice, as it has more effects and sounds for the more club orientated person,
if you are just wanting to practise in your bedroom, or do the occasional gig, you would be hard pressed to beat the Aero,
If you can, go and try both to see what you think.