Well I already have done the math proving that fire 100 will hit slightly more weapon skill damage than lightning 100 and a good bit more nuke damage, and don't feel like reposting right now
But in incredibly brief terms, you can average fire imbue low~high and compare it to the same with lightning imbue low~high and you will find that it's approxomately 18% stronger, so the buff and imbue cancel each other out for base damage, and on top of that fire gets phy boost and stronger nukes so all hits are stronger.
Personally, I prefer the things fire gives you too, such as earth fire, fire wall, and fire shield...seem to give much better advantages than that of lightning. And you don't really need the speed for pvp anyways because you are as long range if not longer than pretty much everyone you'll ever be fighting.
So yea, fire. As for hybrid, I'd personally recommend hybrid due to the fact that otherwise you really have no good defense feat...spears have hp, s/s have shield, but all you have is a chance at knockback. Also, the fact that you crit a lot makes hybrid deal extra damage so it's definitely not a bad idea.
Side note: 105 cap, with 330 mastery cap, you can get max pach/fire/ice and on top of that level 15 lightning so not only will you have already stronger than lightning strength, but get 5% more :P