If you must use only the internals for rehersal type things, I've heard some decent recordings using the cardioids on the H2n.. so in your case I'd be tempted to go that way, even though it is not a very popular choice for most of the recordind done around here I've never used my DR2d internals for this so I don't know how they'd compare. I would choose directional built-in mics and not internal omnis, which are simply not setup to work well on such a small machine.
Just to be clear, the cardioids on the DR2d are not X/Y coincident and I don't know of many built-ins that actually have truely coincident mcis, except for some of the Zooms, most are near spaced and somewhere between X/Y and the popular setups used around here with a bit more spacing between external mics, but that's all academic and not as important as the quality of the mics themselves.
The surround option might sound very good if you are only recording for yourself and your own enjoyment, but the files will be difficult to share, and even if you can people won't know what to do with them or how to play them. Mixing down to stereo form the multichanel files can be tricky as well, but if you enjoy the challenge, you might give it a try. I'd avoid the built-in surround option if your target is a stereo file without too much work that anyone can playback.. and I say all that as one of the few around here that record in multichannel surround.