I just went through the same exact run down that you're faced with. I've replaced my Sony with the Gateway, and have extensive interaction with Dell based on work and other's who have had to contact Dell for support.

With Sony I couldn't get real answers about the computer from the local sales personnel.

The Dell I was considering purchasing (mostly due to the 20% discount from work), but when I spoke with the sales reps and said I would call back after thinking it over for one night when I called back they never returned my voice mail to complete the transaction and I remembered that it took an act of God for the service center to assist unless you buy the horrid upgrade in service support.

The Gateway personnel truely surprised me, not only did they speak with me, they ran through an online chat to explain the differences. I was also astonished with the upgrade costs (they were mostly 20 bucks each, whereas with Dell they ran 40-500 dollars). The onsite service was only 79.00 and after all of my upgrades I walked away from the transaction with 1294.00 (before 100.00 rebate and taxes). I also received the computer within 5 days (3 days before expected).

The bottomline. I have a solid, light, decent looking computer with piece of mind that I picked the right computer.