I say MVAM as in either advanced escort (I fly the original verison).
As for beams well a decloaking DBB BO3 with HYT2 and 2DHC of CRF2 at point blank range, yeah it works and gratifiying when a cruiser is sitting still and it pops before it has a chance to buff. Now I've moved away from the alpha strike, like I said, I've thought of taking it off. Even so I've heard many people betting beam escorts to work because they can fire more consistently. That's not to say it doesn't work for everyone though, I prefer cannons.
I've never even cared about Beams shooting me... They are never a threat... They are just so weak by comparison to Cannons. The ONLY time I get concerned about beams is when a SciShip is shooting them because you never know what they are actually shooting at until you find out the hard way.
I fly MVAM AE because i like Prometheus, but IMO its slow, less punch than Defi-R. Yeah you can seperate, but if u die, you need to wait couple min to seperate again and get boost. And seperating has drawback too. So i fly AE for fun, on my alt i prefer Defi-R. Agile, fast, strong.
I find the MVAE and AE MVAM both superior to the Defiant-R in sustained combat. The Defiant does have slightly better base turn rate and a superior opening alpha strike as it decloaks, but if it fails to kill its target quickly, then the situation rapidly degenerates into an attrition match. The MVAM ships both have 3 sci BO abilites available vs the Defiant-R's 2, which gives the MVAM's a defensive edge in a dog fight. Once the MVAM separates, then the fun really begins. The beta command section easily out-turns and outruns a Defiant-R, and two sub-ships both employ beam overload3. The Defiant-R's cloak is better at ditching chasers and optimizing alpha strike range, making it a superior ambush predator, but the MVAM's are better rounded dog fighters.
As far as the fleet escort is concerned... I don't remeber the last time I lost to one while using an MVAM in 1-1 combat.