Suggest between Dell 7520 and Dell 5521 laptops?

Hi, i am looking to buy an official laptop to make it use as a personal as well as for official use. And as per my budget constraint i came to finalized two laptops which i found better and also i am preferring dell because dell laptops are very good. I wan't to know that between these two Dell 7520 and Dell 5521 which one should i buy please read my constraint first and then suggest
1. It should have a powerful processor.
2 Must support 2 GB of more RAM
3. Battery life must be up to 3 hours.
4. It should be good in looks'

Please tell me as soon as possible. thanks in advance.

Both the laptops are good in their respect and if price is not your concerned then i would suggest you to go for Dell 7520

Nice configuration in Dell 7520 i will also suggest the same.