There seems to be a common misconception that if you're carrying an electro or even a mech semi, for that matter, that you're automatically relegated to a "suppressive fire," high-volume, 'spray and pray' style of play -- and that by choosing a pump, you're automatically going to be a much more "tactical" style of player. A semi can be shot slow and carefully just like a pump gun -- but a pump can't shoot 15bps (with the exception of a very few custom jobs.) I just had to throw that out there.
In reality, all a pump gun does is force
you to play a little more tactically, since it takes away your ability to rely on a high-rof crutch. They do tend to be lighter and thus, you can move marginally faster, but trust me - you can play just as or more aggressively with a semi. (And I'm talking about movement and play style, not ROF).
So really, if you're having a hard time not relying on the "sit back and spray" method of play with a semi, then I'd say going with a pump gun would be a great way to train yourself out of that. Other than that, a pump gun will force you to develop your aggressive side, since you're much better off closer to your opponents.
Hope that all makes sense.