Sharps are better units than sony's (i have 2 MD-MS722 's that have easily recorded almost 1500 between the 2, and sonys i have an mzr30 and one of those new black ones that's installed in my car). The Mic In on MDs isn't very good, btw, so you just want line in anyway.
If you find the 9.24.02 bruce springsteen kc show I taped it's done w/a sharp MD - most of my shows are, actually... But yeah. I like sharp the best. The on the fly level is remembered from disc to disc. Also make sure that your volume is turned down to about 20 when you record, because then if it seems quiet you can turn it up while listening. If you leave it at 30 you have no way of turning it up.
and the 2 second gap in the beginning of the disc will make your disc flip time drop from 35-42 sec down to 13-22 sec.
or you could just get 2 decks.