transferring files

Rekordbox writes a lot of files per track, not just the track like Finder does. If you have a slow USB "write" speed, you will be screwed. Rekordbox creates a lot of folders and wave info per track, Finder is only copying 1 track.

definitely buy a better, faster USB stick, I have a USB 3 with roughly 70-100MB/s write speeds, I copy thousands of tracks in under 30 minutes

^^ that.

I have high quality USB2 drives that beat the pants off generic USB3 drives in terms of transfer speeds (read and write). Just because a drive has a certain spec, doesn't mean it's going to perform. Spend a bit more, save the hassle.