Let's first assume two things:
- You're playing White 2
- You're able to trade
Electivire is not otherwise easily obtainable, so these stipulations give it the best chance of success in this comparison. Unfortunately, its opponent is Magnezone, who is the best Electric type in the entire game. Sorry Electivire.
Magnezone is available in the Virbank Complex and walls Roxie and Burgh right off the bat. Its Electric/Steel typing gives it an obscene 13 resistances that let it trivialise most other important Trainers --- it only really struggles against Clay, Marshal, and Iris. Its base 130 Special Attack and Sturdy make it useful in every battle, and the icing on the cake is SonicBoom to shred the early game. Its main flaws are its mediocre Speed and lack of strong STAB moves, but Magnezone is so strong in other departments that these are easily overlooked.
Comparatively, Electivire has high enough attacking stats to run its wide mixed movepool, which gives it more diversity than Magnezone has. This is about where its advantages end, though: you're stuck with Elekid until Level 30, you can only evolve Electabuzz after the seventh Gym, and Electivire's inferior typing gives it fewer advantages against important Trainers.
It is worth mentioning that Eviolite Electabuzz has higher Speed than Electivire and can be a viable substitute if you can't trade or want a faster Pokemon. It's still worse than Magnezone though.
Magnezone completely stomps Electivire thanks to its typing, advantages against important Trainers, and ease of access. Don't think Electivire is weak though --- it's a capable Pokemon that happens to be worse than Magnezone. But in Black 2 and White 2, what isn't?
