Both my buddy and I are approaching lvl 50 and I went escort and him cruiser. I love the Defiant class and was planning on upgrading to the retro when I hit 50. He is planning on getting the Galaxy X. I am thinking that even though he will have that massive phaser lance cannon, I could easily stay out of it's firing arc. I don't know how the cloaks will work in combat, since we will both have it. Right now, I can destroy his Galaxy 9 times out of ten with my Defiant, but I don't know if I will be able to against the Galaxy X.
The phaser lance is useless against an escort unless he can immobilize you. I think the turn rate is actually worse than the galaxy's. The galaxy- would be a better match but I'd still take defiant. If he wants a defiant killer he needs different ways of stopping you. Tractors gravity wells and the nx01 grappler
Stay in cloak until he decloaks. Then go at him from his weakest side and stay there. It's game. The Galaxy-X's Phaser Lance only comes into play when the X's opponent lets it come into play, by allowing the X to get into that 45 degree firing arc.