In my experiences I find this:-
Recursion:-
James your right mainly it always starts this way most of the time, but we had what I call 'The IP Wars' recently which gave Mervs the advantage. Several names pop up for me from Zion that fought in them and it was really the era where for once we saw Zion fight against the Zerg. Personally I loved 'The IP Wars' (It still exists partially with skirmishes breaking out every so often). It taught alot of us, that we can't use Zerg tactics anymore we had to learn against it, and we really did see who the true pvp'rs were... the guys that stood and fought that is.
Biggest PvP: Zion
Vector:-
Like Gretyl said this can be open, I am yet to see any BIG battles, but as Gret said there are alot of skirmishes. The thing that sets Vector off, and which I do like about it, is the smack talk. No one does it like Vectorites, and the egos out there are a match for my own
It's got talent out there, but their fashion dress is mainly resistance.
Biggest PvP: Merv
Syntax:-
JUMP JUMP JUMP, it's all I see! This server is okay I guess, but there are alot more noobs. The prime factions being Exploits and Foxhound, seem to be the masters atm. However I personally find that the pvp is less wanted maybe. I've sat as a level 2 flagged for about 20 mins b4 with mervs just watching me, okay fair do's there were alot of zion, but still its a level 2. I see alot of jumps in this server and I am shamed to say its Zion
I'm zion on rec, merv vec, and a whole host of things on shimtax, and personally all I see is Machines trying to compete with Zion jumpers. As for mervs they dont even fight here 
Biggest PvP: Mech
TH