PvP is where Guild Wars shines. Global World Championships, PvP skill builds and strategies, teamplay tactics, coordination, role execution etc...
Of course the single player game is also fun, but the PvE part in Guild Wars is more like a action RPG. When you finish it, you finish it.
In Factions on the other hand the developers created new PvE types that offer more replayability like so called Challenge missions that will keep best scores (like defending from waves of mosters on a timer kinda missions), Competitive missions where multiple teams try to reach a goal (RTS elemets) and of course Alliance Battles (4+4+4 vs. 4+4+4) for control of cities, outposts, the world map and access to Elite missions.
The game is definitly evolving and this is just the beginning.
So yeah, check it out. Definitly worth even if you just play thru the new story line and get like 50+ hours of gameplay out of it.
This comment was edited on Apr 27, 15:25.