"Lenovo" or "Dell" Which one is Best?

Hi everyone! I'm about to buy a new PC from UAE ! my budget is around 600/650$ & I got interested in two offers in uae.souq.com .. ( I use the PC for some coding, PhotoShop & illustrator & a bit of video rendering & I'd like to play few games if possible) .. The first offer Is :

1- LENOVO IDEAPAD G510

•Processor: Intel Core i7 4700 4th Generation
•RAM: 4 GB DDR3
•HDD: 1 TB
•Screen: 15.6 Inch
•Graphics: 2 GB VGA :(
•Others: 802.11b/g/n, Bluetooth, Webcamera
•Operating System: Microsoft Windows 8

2- DELL INSPIRON 15R

DELL INSPIRON 15R-3537
Core i5-4200U 2.6GHz

•RAM:6GB
•HDD:500GB
•SCREEN:15.6 Inch,Touch Screen
•COLOR:BLACK
•Windows 8

graphics not written in the offer

* QUESTIONS:

1)Which one is best in your opinion ?

2) Is there a big difference between i7 & i5 ?

3) Can I upgrade the Win8 to the latest update .. (both come with warranty) ?

4) any suggestions

THAAAAANKS A TON!