From the ones you have shown I would go with the Acer. My brother, my g/f and myself have all bought acer laptops this summer from memory express and they are great.. haven't had a single problem with any of them.. I would check there if you are going to buy an acer as they most likely have one in your price range and it will likely be about $50 cheaper than the same thing at futureshop
Just taking a quick look at the Dell site and they have a decent one for under $1000.
http://www1.ca.dell.com/content/prod...HS1&l=en&s=dhs
The core duo processor and extra video card memory will make it easier to run vista in the future.. i dunno how easy it is to upgrade the ram on a dell