Laptop buying advice forum: Sony Vaio S Series vs. Customized Dell Studio 14 laptop

I am in the process of buying a new laptop, and after much research I pretty much have it narrowed down to the 2 computers listed below, but CANNOT make a decision because the pros/cons balance out. PLEASE HELP!!

I am in graduate school and use my computer 24/7, so I need something reliable. My main functions are basic (I'm not a gamer and don't do extensive video editing, but I am always multitasking)- mostly Microsoft Office applications, internet, high volume music & photo storage, etc.

Sony Vaio VPCS111FM/S Specs:

Weight: 4.4 lbs
Processor: Intel Core i5-430M (2.26GHz, 2.53GHz Turbo mode, 3MB cache)
Battery Type: 6-cell lithium-ion (up to 5 hours)
Display Type: Widescreen LED backlit (1366 x 768)
Screen Size: 13.3"
System Memory (RAM): 4GB (DDR3)
Hard Drive: 500 GB SATA (5400 rpm)
Optical Drive: Double-layer DVDRW/CD-RW (not slot load)
Graphics: Intel Graphics Media Accelerator HD
Video Memory: 2263MB total available
Wireless Networking: Wireless-A+B+G+N
COST = $1485 with 3 year warranty through Geek Squad
(Pro = Best Buy warranty includes 1 time battery replacement)

Customized Dell Studio 14 Specs:

Processor: Intel Core i5-520M 2.40GHz (2.93Ghz Turbo Mode, 3M cache)
Memory:4GB Shared Dual Channel DDR3 at 1066MHz
LCD Panel: 14.0 High Definition (720p) LED Display with TrueLife & Camera
Video Card: ATI Mobility Radeon HD 4530 512MB
Hard Drive: 500GB SATA Hard Drive (7200RPM)
Wireless: Dell 1397 Wireless G
Battery: 84 WHr 9-cell Lithium Ion Primary Battery (up to 8.5 hours)
Combo or DVD+RW Drive 8X CD/DVD Burner (slot load)
COST= $1250 with 3 year warranty through Dell

Here is my dilemma:
I own a Sony Vaio FZ series laptop that's about 2.5 years old and its falling apart, so I am a little nervous to purchase another Sony. However, the Sony above has several advantages over the Dell, including: the weight/screen size (I am looking for light weight and portable) as well as the Geek Squad warranty (I don't have to wait on hold for hours with an outsourced Dell technician who reads off a script if something goes wrong). However, it is more expensive by almost $250 and not as good of a machine overall (slower Hard Drive and processor speeds, less battery life due to 6 cell battery vs 9 cell in Dell, screen resolution and graphics card are much better on Dell). I read reviews on the Sony, and the biggest complaints are about the sound and screen quality, as well as loose battery. The Dell is a better machine overall- and for less money- but I'm not sure everything on it is a necessity based on my needs (the Sony might suffice). Dell is also a pound heavier and has an inch bigger screen (a con, although not a deal breaker).

So the question is, do I eat the $250 and go for the smaller, lighter weight Sony with the better warranty and give up some performance and battery life, OR do I go for the cheaper, higher performance Dell and give up some portability, and hope I don't have to use the warranty??

Any help would be appreciated!!!