There are a lot of laptops in the dell studio series. And you didn't even mention the type of work you'd be normally doing on your laptop.
But I'll be comparing the two 15inch $900+ models.
Before I start, let me tell you that if you expect any of these to be able to play the latest games at high settings, then you'll be disappointed. These aren't really gaming laptops, they are better suited for watching movies, doing multimedia work such as light video editing and even drawing on your pc, and playing games at medium to low settings.
Now first the Sony Vaio. The model I have chosen is SONY VAIO E Series VPCEB17FX/W. It's a pretty neat model, priced at $959.99 + ofcourse extra for shipping if you'll want to order it from the internet. It has an Intel Core i3-330M(2.13GHz) processor and a15.5 inch screen with a full HD (1920X1080) resolution that's just about perfect for watching your favourite movies at HD. It has an HDMI port ofcourse so you could plug it in to your HD tv and watch stuff there if you wish. It's got quite a lot of horsepower as well. It sports an Intel Core i3-330M(2.13GHz) processor 4gigabytes of fast DDR3 memory. Plus it also comes with an ATI Mobility Radeon HD 5470, which is an entry level direct X 11 graphics card and has about 512megabytes of dedicated video memory. Good enough to run the latest games at low to medium settings fluently enough. Though Older games can be played at higher settings. It has two memory slots, so you could even upgrade it to 8GB, which is the maximum amount it supports. It has one 1 x ExpressCard slot,three (USB) 2.0 ports, 1 (eSATA), one 1 x VGAVideo Port, 1 HDMI port and 1 microphone and headphone jack. And its got a 500GB 5400rpm SATA HDD. Not bad at all eh. And all that, with around 3.5 hours of battery life and at 2.68 kg its pretty light. So I think this is a pretty neat laptop, good for carrying around and with a pretty good configuration at that.
Now onto the Dell. It's the Dell studio studio 1557.
The Dell is nearly similarly priced $949.99 + shipping fees, should you choose to buy it online or something.
Now the Dell has a 15.6' screen , though it doesn't natively support a 1080p HD resolution. It comes with an Intel Core i7-720QM processor, which is supposedly better than the Core i3 one in the Vaio. The Dell too has 4GB of DDR3 memory and like the Vaio supports upto 8GB of RAM. It has a ATI Radeon HD 4570 graphics, with 512 MB of dedicated video RAM. Though the one in the VAIO is a bit better, particularly since its newer. The Dell has a 320GB SATA HDD, which while smaller than the one in Vaio is actually faster at 7200 rpm. Unfortunately the Dell only has 2 usb2.0 ports, quite a no no if you use a lot accessories that depend on the USB 2.0 ports. But an USB port extension could remedy that. It has an HDMI port and a card reader, and more or less the same ports as in the vaio. It weighs around 2.5kg, but I've heard some people say that its kind of heavy. But I can't vouch on that since I haven't used it myself. And it is said to have a pretty decent battery life of about a bit more than 5 hours, since it sports a 9cell lithium ion battery.
Both run Windows 7 64-bit.
So yeah. Summarizing, it the Sony Vaio is a great looker with a pretty decent display and configuration. The Dell on the other hand has a slight advantage with the Corei7 processor, though it wouldn't make that much of a drastic difference. The Dell has less space, and has fewer USB ports. But it's longer battery life means that its more well suited for traveling around with than the Vaio. The battery life wouldn't be a problem for the Vaio if you don't need to use your laptop at a place where you can't connect your charger, like in a park or field or something. Hmm. I described both of them to you. Now its yours to decide.
Though the dell is like $10 cheaper than the Vaio, idk, I think the Vaio's a pretty neat laptop. Since you asked if a Sony Vaio E series laptop is good enough to buy, I'd have to answer that yes, it is good enough to buy. Though when compared to the dell studio I mentioned above, they're more or less on par with each other. So yeah.
Good luck with buying your laptop!
Hope this helps