Decisions, decisions

Having decided to move away from WoW, I'm now kinda between games (even if I do still have access to WoW until October). I've been looking for the cheapest way to get ahold of CoH, and I think amazon is it (at the moment anyway). So sticking it in my basket, I found all three Guild Wars boxes, that I put there a while ago while pondering whether to keep going with WoW.

Of course, I don't need all three in the slightest, I only really need to get the one. But which one?

From what I can gather, in general, the differences between them are 1) the plotline of the game, b) the classes availible and III) the abilities each class can potentially get.

Now of these, the most obvious is the character class. With this in mind, the choices boil down to: default set, default + Assassin and Ritualist, or default + Dervish and Paragon.

Now, I'm not really a paragon-y person, and dervish, scythes, woo, not that great an appeal, so it looks like Factions is the one for me.

Of course, there could be other wildly different things between the campaigns, but I don't actually know what difference they make, so I'm going to throw this out to the (not many) people who read this:

Which Guild Wars box do you recommend I get and/or avoid? Why? Optional bonus question: should I just wait until GW2?