If mobility is a big factor in your decision, then go for a laptop. Dell XPS are good.
If you aren't concerned about moving around, then for the same price you can get a much better desktop. I'd personally build my own as others have mentioned.
Personally, I'd recommend a mac, but as that seems to be a little out of your price range, HP pavillion's are great but if you're looking for a step above an HP check out Lenovo.
Well if you are not into gaming I would say laptop as it just makes more sense. I use to be into gaming a lot so I had a desktop but I dont do that as much anymore. However if I still want to, my laptop is powerful enough to handle it.