M6R - 3U rack with 100 patch memories - all of which are user editable and savable from front panel. Bi-timbral / split keyboard ability.
M1000 - 1U rack with 1000 patch memory: 800 ROM only and 200 user via SysEx.
The M6R was my first rack mount synth. The parameter legend is printed on the top of the unit and you cannot see the list when it is installed in a rack. You will need to have a parameter chart handy when you're first starting out. After you've spent some time with it, you'll get a feel for where all the parameter are. There's no data slider, but +1/+10/-10/-1 buttons for fine and course editing. But if you're going to use the Kiwi editor, that shouldn't be a major concern.