March Madness is sort of strange. I like it, but there are still problems in their stats and ranking systems. I haven't played ESPN's game yet, but I can imagine it's a bit better if you want realism. Also, the gameplay on NCAA is something that takes awhile to get used to. Inbounds passes are a bit different now, and the two shooting buttons (layup or jumpshot) took me a bit to figure out. The pro-hop is nice, but takes a few games to start using effectively. I like it, but I'm still interested in playing ESPN's game before I buy one of them. Seems like on MM you can easily get into a funk where nothing is working. All your passes get picked off and it becomes frustrating. Not necessarily when the other team is at full momentum either.
From the articles I've read, it really sounds like ESPN is more difficult and you will have to learn plays and execute more precisely on offense. Personally, I like this idea. However, when playing with friends, I can see how MM would put you both on a more even level. Basically like the difference between Live and NBA2Kxx.