Both are great but do you mean Mk. 3 or BIII for the second listing? Big difference there! One is a console B!! and one is a stand-up model, which is the current one they sell.
BTW, The MX-55 is cool in that it does 30 IPS. I have a MX-5050 BII, a MX-5050 BIII and a MX-5050 Mk.3 console if you need help with those---all great machines!