Both creations are very, very nice, good work. However, the mech's body seems to be a little wide- not that that's a bad thing, mind you, it actually looks pretty good, it's just that with something that wide, it seems like there should be more than 1 clone in it (Kind of like the old MTT Alt. Mod). The cannon also looks very nice, although I'm not a big fan of the technic beams, you should probably replace those with white bricks. The only trouble with that is then it would look rather plain, so you may also want to greeble it up a bit- just add a few details to break it up a bit.
Other than that, these both look very nice, I think you did a great job with them. Keep up the good work!