I think there are a number of secondary differences, in which I would score these two games as follows:
* Map travel (GW +1) vs. conventional travel (WoW -1)
* No Auction House (GW -1) vs Auction House (WoW +1), etc.
and primary differences such as:
* Crafting (WoW +2) vs. no real crafting (GW -2)
* Monthly fee (GW +2) vs. subscription (WoW -2), etc.
In terms of general PvE I'd place the two games on about an equal level.
In terms of PvP I really can't compare them cause I don't PvP ... ever.
The really
major difference between the two games, in my opinion, is in regard to the handling of instancing and all that instancing entails. If WoW ever made it so groups of fewer than 5 players could run instances, either by scaling the dungeons to party size or by adding summonable NPCs, so that such groups had a fighting chance of completing the dungeon, that would probably tip the scales for me in favor of WoW: in other words, if Blizzard somehow retooled their instance content to make more of it accessible to 1 to 4 human players.
This is where GW really outshines WoW as far as I am concerned.
Take, as an example, Sorrow's Furnace. SF is a fair example of a "WoW-like" dungeon that exists in GW. There are multiple quests in SF that can be run in succession in one sitting or stretched out over several days. You can complete the quests with friends or on your own. You can pause in the middle of one, go out to dinner, and come back and finish it later. You
never have to worry about finding a group, regardless of your profession or build. In all of these ways Sorrow's Furnace outshines, in my opinion, the instance/dungeons in WoW. In terms of actual
dungeon design, WoW rocks. But in terms of dungeon
accessibility/playability for all players and playstyles, GW rocks.
I only wish the 18 "unique" EotN dungeons had been more like SF ...
It would not surprise me at all if the folks at ArenaNet are really planning, in GW2, to incorporate the best of both MORPGs (WoW and GW) into a single game. How effective they will be remains to be seen, but I am
really looking forward to seeing what they come up with.