As Mechwarrior 2, or rather Earthsiege, IA is also mission-based and before every mission you can choose a robot and it's equipment as you want. Controls are very simplistic, you may not even know half of them and still win.
Graphics are not true 3D, but a combination of 3D world and sprite characters. Levels are partially destructible - you can damage surroundings, street lamps for example. And a really notable thing about Iron Assault is cut scenes. They're made using very unusual technique for computer games - stop motion animation(just remember classic King-Kong movie).