which is the best buy

Go For This As It's A Bigger Brother Of The 610 But The Bit Difference i notice is the physical buttons in 710 vs the touch capacitive buttons of the 610. that you have to see which one you prefer. Or check Out The SONY XPERIA U. It's in a similar price range and if would prefer android go for this one Dude.

Good choice to buy a windows phone. Its a very good smart phone with good processing speed without any lag. Till now there is no complaint about the windows mobile.

Hey Aron, they're very similar since they come from the same line of phones, so it really depends which features are important to you. You can see some of the tradeoffs for each phone using our compare phones feature here: http://sortable.com/phones/Nokia-Lumia-710-vs-Nokia-Lumia-610 - Personally I would go with the Lumia 710 but if you can hold off until November, the Lumia 920 is looking like a really strong phone. You can check it out here: http://sortable.com/phone/Nokia-Lumia-920

The Nokia LUMIA 710 is better than the 610 in most cases since the 610 was aimed at the younger crowd. If you can wait though, I'd wait till the 920 comes out. If you want WINDOWS 7 though. I recommend saving up for the 900.