Ever since I've started preferring lighter systems, Chris Perrin's Mecha RPG has become one of my favorites. Combat is still tactical enough that your choices matter, and there's just enough differentiation between different mecha to make any two characters (and their mecha) distinct in their combat styles. But it's definitely a much simpler system, and fairly influenced by indie design elements like scene framing. I've ported Heavy Gear to this system and it works great. Highly recommended.
[4 of 5 Stars!]