While AGS really is more the retro-engine I don't think that AGS is more for "Sierra games metality" as said before... You can create games that look exactly like old Sierra SCI games but you can also copy a Scumm Interface. I'm working with AGS and I prefer the old Scumm look of Monkey Island 2 oder Day of the Tentacle - and you can rebuild something like that perfectly with AGS. And I've also seen AGS Games using the "Coin Interface" used in FT or MI3. The template game uses a Sierra SCI lookalike interface but you can download lots of other templates to orientate on whatever retro-syle you like or create your own.