Taperssection.com and minidisc.org have reviews and info.
The 910 comes with a 900mAh battery and the MZ-RH10 comes with a 1450mAh battery and has a backlight.
The MZ-RH10 has an small external AA Dry Battery Case that you can connect to the recorder.
IIRC they are not Mac compatible (via USB-the software is PC only, though if you have a intel mac, fresh WinXP SP2 disc and BootCamp it might work), don't have a line out (only headphones out), and have some kind of DRM protection (I think only for mp3 though).
Also pretty sure that a WAVE (or AIFF) is consistent across platforms, so where 24 bit/44.1kHz on a 2GB card = 125 minutes, a minidisk at the same rate will get you 62.5 minutes on 1GB of storage. By the time you downsample enough to fit 180 or 240 minutes you're down to mp3 @ 320k. Mp3 is great for the web, but for RedBook audio (audio cds), you'll have to convert to WAVE/AIFF on the computer.
I'm using an AT-822 (stereo mic about $250) into a Edirol R-1 ($425) with a Sandisk 60x 4GB Flash card (about $180 @ TigerDirect.com).
The Edirol R-1 has a 2GB/2 hour storage limit bug: You have to start a new file at that point. It also can't monitor levels while recording (I put it in standby, do a level check or just start it during the first tune after setting the levels). This bugs me, but as my old and beloved Sony Walkman Pro tape recorder took one too many falls off a music stand, I had to go with what was available.
On a Mac the R-1 is usb plug and play, I use BIAS Peak LE when editing is needed (eg: too lazy to start and stop recording between tunes).
Their new model is the
R-9, which _can_ monitor while recording, no reviewer verified info on file size/time limits yet and it uses a SD Card (supports 64 MB?2 GB),
they claim 110 minutes @ 24/48, 180 @ 16/44.1 and 797 @ mp3 320k. Some may have shipped but most retailers are now saying June delivery.
Even w/o a break in a 3-4 hour set you should be able to find time to start a new file (R-1) or swap the memory card (R-9), at the 2 hour mark.
Everything I've read says to stay away from the M-Audio MT.
Good luck and let us know what you go with!