The main difference seems to be that the Prime model includes start/select buttons. I use a keyboard for navigation so that hasn’t been a big deal for me, mine is the EX Pro. There’s a detailed comment here for additional differences (sorry it’s on reddit): https://old.reddit.com/r/DanceDanceRevolution/comments/1iqrrtn/new_and_clueless/md33x8k/

I highly recommend L-TEK if your budget allows: https://www.iamats.com/

I have one for DDR and one for PIU, both have been great.

They are not being manufactured anymore but it is still possible to buy new old stock. One guy is trying to keep them in circulation (he owns floppydisk.com) and I found a somewhat recent article that has some good info as well: https://www.raconteur.net/technology/the-floppygeddon-cometh