You cant really factor in asteroids into the equation because theyre made randomly, coming at random angles at random speed with random size.

But we in our Rebel cruiser can maneuver behind them in evasion of the Confed torps and missiles.

"We in our Rebel Cruiser"?
If there were asteroids, why would a Confederate brainlessly unload torpedoes on you? Save it for close range.
-Bob

i've found that a properly upgraded scoutship will readily take on both simultaneously in a me vs. AI fight. using my tactics, i would have to go with the rebel cruiser, i'm better at strafing and baiting than waiting for my opponent to come to me. and i have to say, those heavy rockets are darn useful. even after you come in with your 30+ torps, you can still throw in your 2 or 3 rockets before you leave. each one of those is a lot better than a torp. also don't forget about the torps you can throw back after you pass the confed cruiser.
but, as i said, that's just with my tactics and that may not reflect the actual performance. i'm just saying that given the choice, i'd take the rebel cruiser.