Magnum also has a new top chassis plate that eliminates the flex in the chassis (something that we all try and mod in someway!) it also lays down the steering servo onto the chassis and gives you a 125cc fuel tank (also a popular mod...bigger tank). And a way better body (IMHO). And the chassis/shock towers are better blue insted of purple.
So in other words its done a few things that you will do to your truck anyway, but I guess it depends on how much the price diff was. I was doing my comparisons on EBAY where the Magnum ranges from $250 - $340 and the MT2 $230 - $330.