I wouldn't even compare the 2 as they are COMPLETELY different styles of games.
The first is a action game with FPS and RPG elements (along the same vein as Earthsiege, Heavy Gear etc), and the other is a straight up action game very similar to Desert Strike.
Be like trying to compare Super Mario World to Super Mario RPG. Completely different.
And for the record, my votes for the original game (which coincidentally was a partial port of the original Mechwarrior for the PC, though the levels and story are quite different).