I find it odd the comparisons people are making between the two games. You're taking the approach of "this apple is bigger than the other apple" when, infact the other apple is an orange. I mean, if i was to ask which is better, CoD4 or FFX? What answer would you give? They're completely different games.
Granted these two aren't quite as far removed from eachother, but they've completely different focuses. Guildwars is more or less entirely PvP orientated, with the exception of the original, you will reach the maximum level VERY rapidly, and it is then about gaining skills and using those skills to create a "build" which is where you set your attributes to various stats, and pick 8 skills for your character to use. With the wide variety of skills available you can make thousands of different build combinations.
PvE in Guildwars IS there, however in my opinion it's rather disjointed due to the ability to just teleport whereever you like as long as you've been there before, and to be honest, PvE is mostly there just to get abilities. PvP is where guildwars really shines, as you can create a PvP character in seconds, giving them weapons, armour and skills you've unlocked. You fully customise them and then go into the fray. The major advantage guild wars has over WoW here is that the PvP is infinitely more balanced than WoW, and there is no "perfect build", for example my Elementalist might destroy a warrior with lightning before he can touch me, however a mesmer might come along and interupt all my spells and kill me without me hurting him. Therefore it's good to have a balanced build and a balanced team that works together and makes up for eachothers weaknesses.
The lack of a subscription fee is also a good consideration.
WoW, is pretty much all about the PvE in my limited experience playing it. I can't claim to have played "end game" however I've seen friends do it, and frankly it looked just as inbalanced at high levels as low levels. Boiling down to either who has the better gear or who is the "superior" class (assuming they are not just plain 20 levels higher than you). However on the flip side, the PvE in WoW is much larger, more expansive, and better in much every way. For all my complaints about the PvP, it's PvE experience is pretty good, and offers probably the least grind of any MMO (whether you consider that a good thing or not is down to you, some people feel it makes the game too easy).
As for which is more "social" i can't really say. I would say GW can be very social if you join a guild and participate regularly, and very rewarding. However given you have several NPC's you can use, and that will get you by all but the toughest missions, there is the option to fly solo a lot of the time, and that might be forced on you if no one else needs to do the mission. As it is instanced you won't see any people outside of towns unless you are in a group with them.
As for WoW, it is "arguably" more social, as you will run into people all over the world. However roughly half of these will be the opposing faction, who will proceed to maim you horribly for having the nerve to be new to the game and not lvl 80, and the other half i found to be relatively antisocial or plain hooting morons. In my time in the game, i joined several guilds, and found them all filled with mindless 12 yr olds (or at least i really hope they were 12), and found that the entire time i spent in WoW was a mostly solo experience. The few times i wanted to do a dungeon where i required a group, i usually got a friend (RL friend) who was a higher level to boost me through it, or the few times i actually played with a group i found them generally rather inept and annoying.
Perhaps i'm just a mean and unlikeable elitest who didn't want to make friends? However i have played several other MMO's (FFXI, Earth and Beyong, LotRO) and never had any trouble finding people i wanted to play with on those games.
At the end of the day it really comes down to what you want, and hopefully my rather lengthy review will help. The long and the short of it is i suppose:
PvP: GW
PvE: WoW
Social: Unsure
Cost: GW
As for the old "Go for guildwars if you don't have alot of time, WoW takes lots of time", i honestly never found WoW to consume more time than GW, i found it to consume less if anything. Granted if you're PvPing you can leave more or less at the drop of a hat, however on WoW it's so casual and "pick up" for an MMO, you can go on, kill shit for half an hour then leave. The only times you'll have issues are in a mission on GW or a dungeon on WoW, and i found i did missions on GW alot more frequently than Dungeons on WoW. As for the self control factor...try to fail at life less?
Hope this helps!
