I use two desktop PCs, one which is my main machine and the other one which is in my teaching room.
I prepare the lessons on the main PC, recording straight to USB Flash drives, which I can then plug straight into the teaching PC.
I've been using this transfer method for ten years without a single problem.

Speed shouldn't be a problem when playing MP3s, even on a PC running XP and USB2. My main PC will play a SEQ file of fifteen audio tracks from a USB3 Flash drive without a glitch - it may do more, but I haven't tried it!

My advice is not to buy the cheapest drive, but go for a quality product and to back up, but you do that anyway.

ROG