The last two companies I've worked for bought Dell laptops exclusively. I really like them. I don't know if it's worth it to you, but if you buy the extended warranty, they'll really work with you to get your computer fixed (they even have one that covers, spills, drops, etc.).
Even if you don't get the warranty, they were helpful with helping find replacement part numbers. The express service code they put on all computers was nice to as it allows you to get decent specs on the computer as it was when you bought it.
I don't know much about Sony so I can't really compare to them, but as a Sys Admin who dealt with Dell for three years, I was happy with them.
I had a dell that was from like '98 that is still up and running -- i upgraded last march with the "basic" Ispiron 1501 15.4" screen and I have yet to have a problem with it! My boyfriend has the same laptop with Vista (i'm running XP) and it gives the same performance except on start up ... the Vista is a little slower to get going.
My dad just bought the new "basic" dell 1525 and its the same great computer with a little bit different look.
For the money, you just can't go wrong with a dell.
I am using a Dell Inspiron 1720. 17" screen. Only thing I do not like is the high gloss screen. It is great for viewing as long as nothing moves behind you. Then it's like watching something in a mirror.
Dell has many discount programs availible on line. If you work for most government agencies or larger companies, you can get great discounts. Mine had over $700 off from list.
I had a Mac Mini for about 2 weeks, had a lot of problems with it not working with other programs I already had, and needed to use everyday. Ended up returning it. Would be great as a secondary computer though... my daughter was really disappointed I took it back, she loved the Garage Band program
It was very nice to work with though, and I was told that I could install Windows on it if I wanted to... but I figured, the reason I got the Mac was because I was tired of windows problems, so what would be the point? Maybe I'll look at getting another one again sometime and installing windows on it, but I needed the laptop for work and I think the Dell will do me good
I have one of the Dell 17" that come in the wacky colors. Vista. It hasn't given me one problem since I got it 7 months ago, and I'm on it constantly. Dell customer service is TERRIBLE though, we've been fighting a fraudulent double charge over a printer for over 6 months.
I bought a Dell Inspiron 1526 2 weeks ago for my daughter to take to Valdosta...250 gig HD, 2 gig Ram upgradible to 4 gig...Vista OS, 2.1 mega-pixel web cam, blue tooth, etc etc. Found it at Staples...last one in the store..manager reduced the price to $531.80. I jumped on it...perfect for her needs!