between the vanilla and ME, the vanilla. The ME has the music player auto-start at bootup and unless you have Handy Taskman or something similar, there's no way to kill it.
I get 19.2mb at boot after shutting down 'Music'. I have Handy Weather running at startup. Without anything installed (except Handy Taskman) I would get around 20.4mb. I don't think there's much difference between the two except 'Music' starts automatically at startup on the ME but you can shut it down with a task manager.
If I'm not mistaken the vanilla will offer more RAM at boot, but the IE is best as it has all the extras of the ME, but if I'm not mistaken it doesn't keep the music player open like that.