Personally, I think the fleet is better for tanking in STF's. I see the advanced as being slitghtly better for pvp, kinda of a in between of the fleet and defiant. If you are talking purely cosmetic, I would go with the Promethues.
I'm rather fond of the Hephaestus saucer/hulls and Cerberus nacelles myself. Can't remember which pylons I used, but forward swept on top, aft swept on the bottom. Put a MACO shield and some Borg tech on it and it just looks like bad things are going to happen to you.
My favorite part of it, if you decide to buy the C-store version, the MVAM console works on both versions, giving you a ship with two different bridge layouts and an amazing special power - all the speed of a Bird of Prey, none of the reduced equipment loadout.
The Gryphon's more durable, since you can set up your engineering powers to harden your hull and shields instead of either or, but I've found three science powers generally more manageable for countering all the things that **** you off in an escort.
The extra engineering slot on a Gryphon means you can run paired Emergency To Shields 1 and have a slot left over for extra tanking goodness (my tac alt's setup). On the other hand 3 sci slots means being able to pack sci team, polarize hull, and hazard emitters all at once and easily counter any debuff thrown on you, or even a super-useful tractor beam 1 if you want. I suppose you could even go for paired TSS1 for tanking if you really wanted. Generally though, engineering toughness versus science versatility.
(Yeah there's APO instead of PH but the APO speed surge throws off my targeting, and PH has a shorter cooldown and works with an ensign slot.)
While the $25 MVAM function is fun to have, it doesn't work as well as it does on TV. I'd stick with the non-disintegrating version because it's a great ship by itself.
The MVAM is worth the purchase for the "option" to separate it yes, but the real benefit for the payware ships is the Lt. Cdr. science bridge officer slot. You can put a decent scientific area control ability like Gravity Well I there making it a multi-role 'science destroyer'.
As for me personally I went with the Fleet Escort as the design simply looks like some far-future Japanese ship or aircraft. Or a very highly evolved "saucer and nacelles" design made to counter 25th Century threats. I like the 'alienness' of it.