Samsung Series 9 vs Thinkpad X1 Carbon vs Sony Vaio S 13.3 Premium

I am looking at a laptop for college. I plan to major in Computer Science and would like the laptop to last a minimum of 3 years. I have shortlisted three laptops:

Thinkpad X1 Carbon: $1649
Core i5 ULV
256 GB SSD
4 GB RAM

Samsung Series 9: $1699
Core i7 ULV
256 GB SSD
4 GB RAM

Sony Vaio S 13.3P: Approx $1550 (with 10% student discount, a free PS3 and a possible Visa Prepaid Card $100)
Core i5-3210M
256GB SSD
8GB RAM
2GB NVIDIA Graphics

All of the above have the same screen resolution and come in the right weight range of 2.8-3.8 pounds ( I have a Dell Studio XPS presently weighing around 6.3 pounds
and so 2.8 or 3 or 3.8 will all seem light to me).

What I like about the X1C is the 3 year warranty it comes with, Lenovo's good customer service (that is what I have heard at many forums) and a rigid build quality.
But it gives an average battery life, cannot be upgraded and as per the prices reported till now, an expensive buy.
The Samsung Series 9 gives a great battery life, a fast SSD and a very sleek design. But it comes with only 1 year of warranty and cannot be upgraded.
The Vaio is great as per reviews, a standard voltage processor, whole array of ports and optical drive, discrete graphics ( I do not game regularly but would not mind
a laptop that gives me the opportunity to play Codemasters F1 2011), a really fast SSD, can be upgraded and a free PS3 (which I'd like to sell and it can act as a
further $200 discount). But its battery life does not match the Samsung's and there are conflicting reports about its build quality and Sony's customer service. It
also comes with a 1 year warranty and to upgrade it to 2 years will cost $150 more. Also, for some reason, it does not seem to have attracted attention like the
Series 9 or the X1C.

At the present prices, the Vaio S seems like the best option as it feels ridiculous to pay the same amount for the other 2 ultrabooks which lack so many features and
just have the thin profile and weight going in their favor (though the Series 9 looks amazing). But if the Thinkpad is sold at a discounted rate on 21 August with web
discounts(like $200 cheaper), would the Sony be worth the extra $150-$250 then?

Thank you