The mech in the foreground is unique, an enormous canon on one side, a tiny, delicate grasper on the other. I like the contrast. Also, the glowing holes in the wrecked ship are very realistic. I don't know what plasma canons would do to a chunk of metal, but I think you're probably close to the truth here. Again, nice work!
Love the tank in the background, very sleek, great scene in general.
Speaking of which, I think a tank would always beat a mech in a one-on-one battle, even though a mech would cost more to build... but mechs still look awesome!
This is really nice, maybe it's just the dust but the sensation of "movement" in the mechs and tanks in the back is really effective. the one tank on the far right doesn't look as blended into the background as the others though. I really like the mech designs though, their gait is very easy to imagine, and I especially love the gimpy little manipulator arm.