I use Vista and I love it compared to XP. Granted there is 1 game I have that got screwed up, but I really don't care. Vista is way more stable then XP for non-business uses. I have heard horror stories of trying to get Vista to work properly with various pieces of business software.
Now, the real thing comes down to what do you really want to do with your laptop. If all you need is standard applications like word, excel, other such programs, then it is a toss up.
Obviously screen size matters, so the dell wins this round.
Reliability/support - Apple probably is better, but I've never had a dell computer break on me. Obviously that doesn't mean much, but I can't really comment on support. As for things happening to laptops, It is all about how careful you are. My family has had 3 laptops, and all have died of old age, not mishaps.
Price - obviously dell wins by $100. It depends on if the tech support is worth this extra 100.
EDIT: I personally would go with the Dell, however that is because I am a software developer and I get free copies of Visual Studio for free from Microsoft.
