Suggestion between Dell Vostro 3500 & Studi 15 Laptops

Dear Experts   ,

After long hours of search, i have narrowed down my choice between Dell Vostro 3500 and Dell Studio 15(Featured laptop).

Both configurations are same and as below

I need to use applications which demands high cpu power but due to budget constraint i have choosed to pick one of the these two    

1. Intel® Core™ i3-370M Processor (2.4GHz, Dual Core, 4T, 3MB L3)
2. 15.6” (1366 x 768) Wide LED (720p for Stuido and High Definition for Vostro)
3. 3GB (1X2G+1X1G) DDR3-1066MHz SDRAM, 2 DIMM
4. 320GB Hard Drive, 7200 RPM
5. 8X DVD+/-RW Drive
6. Intel® Integrated Graphics Media Accelerator HD for Vostro while Studio has 512MB ATI Mobility Radeon HD 545v
7. Vostro has 6-cell Lithium Ion Primary Battery (1 Year Warranty) while Studio has 9 cell
8. 65W 3Pin Power Adapter for India
9. Dell Wireless Network Card 802.11 b/g/n
10. Dell Wireless 365 Bluetooth Module
11. LCD Back Cover Wireless LAN
12. Genuine Windows(R) 7 Home Basic 32bit (English)


I read reviews for both laptops.,
Some say vostro is sturdy and is good performance.
Some say Studio 15 is good performance
Some say Studio 15's fan makes noise when overheated but Vostro fan starts up at 7-8mins and the fan is noisy and never goes down even when CPU process is idle...  
Apart from noisy fan, Vostro is very good.
One guy also said after updating BIOS the noise of fan comes down a little, but though the noise still remains.

Could you please help me to decide which one to buy.
Also please suggest me is it ok to buy Operating System along with this or shall i take just with DOS and i use my own OS after partitioning the hard disk according to my needs?

Please give your valuable advice for my above questions.  

Thanks in advance and i am really eagerly waiting for your help.



Sincerely,
Manjunath