Hopefully I can help a bit....I tried the Deuce, Trident, and Ace 2x12 combo before buying my Deuce.
All great amps...ended up with the Deuce, and here is why...you covered most of the reasons already.
-To me, the 100 watt power section gives everything a little more beef...big transformer, more metal....can't go wrong :twisted:
-HEADROOM....the cleans are cleaner, and the drive holds together better to my ears
-I HATE combos for their weight...especially mesa ones...lugging a 100 lb piece like that is not easy on the back...I'd much rather have it in pieces.
-I've always preferred the sound of a separate speaker cab...the speakers seem to resonate a little better, and you have a much easier time matching the head to what you like cab wise....you're not stuck with it in one piece.
-You might also prefer the response of a close back, which is now an option with the head....more punch IMO.
-Finally....tubes are supposed to lake less of a beating in a head....since they're not in the same enclosure as the speaker....makes sense to me.
So yeah...for those reasons....and just because it overall felt and sounded like a better amp to me, the Deuce became my next amp.
Just an FYI....the Deuce can get slightly heavier to my ears...maybe it's the closed back cab that does that, but it does all the vintage marshall vibe the ace does, and if you want it too, it does aggressive and punch that I couldn't get out of the ace.
Best of luck....it's definitely a fair trade, if not slightly better on your half....the heads seem to be selling better as of late.