It depends on who you ask. If you were asking me, I'd go for Dell in a heart beat. In comparison to Compaq/HP, Dell's are far more reliable and will last you the longest. Plus, I've found their customer support to be excellent. Here's a bit more on laptop reliability:
I use compaq and its quite good and the way I use it, it makes me feel good because it has high scores in it's assessments. I'de better prefer on using compaq since I don't even know what Dell is!!! I am currently collecting HP/Compaq laptops.