The Rosetta is nice if you're only going to be tracking 2 tracks at a time. But if, say you had a singing group with 5 singers on 5 seperate mics who liked to sing live in the studio to get the right blend, then it would hold you back. An AD16 would give you 16 channels at a time, so you could record vocals and a band all at the same time of you wanted to.
Just something to think about, not sure of your exact needs.
H2H