Guild Wars versus World of Warcraft

As a novice gamer, I have looked at various MMORPGs and have found that Guild Wars by Arenanet and World of Warcraft by Blizzard are the two most popular and best quality games. I have only played Guild Wars myself and much enjoy it. It doesn't have the monthly cost as WOW does and has a really fun PvP. From friends and others, I've heard that WoW has a really good PvE and is much more challenging to reach the level cap. I still think that the monthly cost is a little too much though.