When it comes to GPU OCing. You've two options, one is to buy factory overclocked version, the second is to buy a stocked GPU and overclock it thru voltage regulation. Benefit with factory OCed version is that if anything goes wrong you can easily claim it whereas if you are using manual overclocking on stocked GPU you may or may not be able to claim it in case any thing goes wrong.
But now a days, overclocking has become so common that this above concept is loosing. Having said that, it is users own experiences which you'll hear. I've used factory overclocked version and stocked GPU with manual overcloking. Both worked great. This is really upto you now to make a decision.
If price factor is involved pl stick with the stocked gpu and if budget is not a consideration then you may get overclocked one. In EVGA products, there are different OC categories which are superclocked, overclocked, classified and now they've introduced KingPin edition. All with/withou dual bios, ACX cooling, liquid cooling etc.
Stick to the basics and you'll be fine.
Happy Hunting!