It's a tough comparison, they're pretty different games. I've played Guild Wars for more than 2500 hours and I had my WoW account for a month before I got bored.
Guild Wars is a game about skill, rather than stats and loot. You're locked to a maximum of eight skills at any given time, and you can change your stats and skills as you please when you're in a town. It's a really fun game if you like being creative with the way you do things, because there are a lot of skills you can use, but you can only use so few at a time. That's not to say it's hard to find a good build, but it can be hard to find a truly awesome build.
And in Guild Wars, there is very little focus on grind compared to WoW. In GW, the level cap is just there, it's not something that really matters. You'll reach it quickly and in order to get better at the game, you have to figure out how to be a better player. It's not about grinding to a new level or grinding for new gear, it's about experimenting with the way you play games.
For example, rangers have traps, and by choosing a mesmer as my secondary profession, I was able to create a build that allowed me to kill some of the more powerful creatures in one of the big dungeons in the game alone. It's all about refining your skills and knowledge with the game.
That's why I got bored of WoW. When I played (just when BC had been released), it was grind, grind, grind. "Go out and kill these mobs for me" yadda yadda, and I know things have changed since then, but in the end it's still WoW.
There is a free trial for GW, and I think it's definitely worth checking out. It should run on your PC, though it won't be too pretty I'm guessing. http://www.guildwars.com/support/gwtrial.php