I have played WoW and currently am playing Aion. In my honest Opinion, I would say that Aion would definitely be better. They have their better graphics, character creation, the quests, the PvP and PvE is great as well and the dungeons are amazing and can be fun to play on and if you are that kind of person that grinds sometimes, it will be a little more easier. WoW is also okay but in my opinion, again, their graphics are a little cartoonish, they dont show much for when it comes to creating your character to your likeness, doing the majority of the quests can be a pain unless you use Thottbot. World of Warcraft has an okay PvP and PvE and their dungeons can be fun also and Grinding can be a pain.
Like Im saying, I like both games for their ups and downs but I would definitely say you get Aion.
Wait, you're making a case for Aion b/c WoW's grind can be a pain at times?
Well sir, you are entitled to your opinion, but you must not have gotten that far into Aion b/c 30+ sees an astronomical spike in the amount of xp you will have to grind in order to level.
I quit at lvl 30 after needing only around 6 million xp to get to lvl 31. After consulting charts of the xp curve, which spirals up to 140+ million xp near lvl cap, and noting the serious lack of quest content which then drives people to grind in the Abyss where they are then farmed themselves by PK'ers, I told myself no thank you despite waiting for this game for 2+ years and purchasing the collectors edition (oh those CE wings were so nice for all of the 5 days I was lvl 30 b4 cancelling).
WoW's stylized graphics may not be for everyone and the character creation is quite limited, but take out all of the expansions and vanilla WoW still destroys Aion in quest content.
Many times, the quest content in WoW are linked to a chain that start when you enter a zone and build up to a climax by the time you are ready to exit said zone. It does very well for the level grind while providing a pretty good story, which in turn helps alleviate the fact that you are grinding.
Only during the 1-10 Pre-ascension quest line did I really feel that way. Past that, the majority of the quests felt very detached and separate from one another, except for possibly the times when you were forced to group up and knock out the quests that made you venture into the elite camps and that felt more like an open-world dungeon area where multiple groups of people could be at the same time.
Now I know that NCSoft delivered a patch that helped up the amount of quest xp given, but they were seriously lacking in content past 30 to help you through the leveling process.
Also, thottbot has become obsolete since WoW has a built-in quest helper and tracker.
Ultimately it really comes down to what type of player you are.
Graphic preferences aside, if you are an experienced MMO player, both games still apply. If you are newer to the genre or are just a casual player, WoW will be much more inviting.
If you enjoy a straightforward grind, then Aion is something you would possibly lean more towards. If you enjoy versatility in your playing experience, WoW will probably be a better choice.
Aion borders much more on the hardcore side whether it comes to leveling or Crafting or even Pre-cap PvP (I say this b/c aside from lvl 19 pre-made WSG bgs, WoW becomes very PvP hardcore around endgame) so it will be harder for casual and newcomers to get into it.
WoW is much more laid-back and accessible to the non-hardcore until you get to endgame and even then it's still possible to be casual about it.