The Armitage, just for the runabout pets. It makes gate duty on Infected/KA and protecting the Kang on Cure so much easier with all those tractor beams/chroniton torpedoes. And then, you can switch to the Peregrine when you need more DPS.
Each escort is fun to play, and every subtype excels in some areas of the game.
From a pure DPS/survive PoV fleet escorts are great, and for free.
If you don't mind paying cash (like me), the MVAM is great in its diversity during combat, with the right BOFF Setup (CC, DPS, bit crossheal if you really want to).
The Armitage is great in changing roles between combat, and though it has a rather odd BOFF-layout, it makes tanking this tiny bit easier which allows you to go aoe everywhere (something for FX junkies like me ).
Defiants are fun for pure DPS, and with the S6 update to Quad Cannons I will start flying my lady again.
ATM I prefer the Armitage, just because she is new and shiny.
(Call me a girl for that, if you want )