Well, I can't give you a great answer, since I know next to nothing about Maryland. However, I grew up right near SB and both my parents are alums, so I can give you some impressions on that.
SB has a lot of research going on on campus, as well as the resources at University Hospital, which has a level 1 trauma center, an upper level NICU, etc. I think it would not be overly difficult to get involved in research, as I did reaserch in two different labs at SB when I was in high school, and have friends who worked in several others. You might want to find out about the developmental bio lab - there was a lot of good stuff going on there when I was looking for a lab, and they seemed very interested in teaching.
My dad was a pre-med there, and though this was 25-30 years ago, you should know that he found very little support, didn't do well in the pre-med classes, and did not ultimately go to medical school. Of course there are stories like that everywhere, but i get the feeling it happens more often at large state schools like SB (and probably also at Maryland).
All I know is, my dad was dying for me to go to a much smaller school, with more personal attention, better advising and tutoring program, and if possible, a combined degree program. So I did, and it's been great.
Not sure if you've visited stony brook. The town is quaint and pretty, as are the neighboring towns of setauket and port jefferson to the east, and st. james to the west. These towns are affluent, and it shows for the most part. Town gown relations are iffy at best. You are very close to pretty (but rocky and calm) beaches. You are not getting to any of these things unless you have a car, or know people who do. Though most people do have cars, since they commute. Parking is, of course, horrendous.
I don't think I'd pay out of state tuition to go to SB. Have you considered SUNY geneseo?