The only quantifiable "con" to an electric conversion is initial cost... Unless you buy the cheap chinese batteries/chargers. If you stick with name-brand stuff, it gets expensive quick. The other cons are merely subjective like the lack of noise and the smell of nitro (which is actually a pro in many peoples' eyes).

Electrics are faster, cleaner and quieter. But for me, I like nitro because of the added challenge of tuning an engine. To me, a gas/nitro engine is what makes this hobby more of a true motorsport rather than just another hobby like stamp collecting