Acquiring a new graphics card

I was thinking of getting a new graphics card since my old 560 Ti feels rather sluggish sometimes and the thought hit me. What's the point in getting the more expensive version of the same/similar card (Lets take nVidia GeForce GTX 760 for example) that just has a higher clock speed. Surely you could just over-clock the lower priced card.

Two examples:
Lower priced card: http://www.dabs.com/products/msi-geforce-gtx-760-1006mhz-2gb-pci-express-3-0-hdmi-oc-8SY6.html?q=760&src=16

Higher priced card: http://www.dabs.com/products/zotac-geforce-gtx-760-1111mhz-2gb-pci-express-3-0-hdmi-amp--edition-8SMS.html?src=12

I know Black Friday and Cyber Monday are coming up which will obviously make these cheaper, but I'd love to know that this (Get a cheap GPU then OC) would work in the future. Obviously things like different cooling systems can make a difference but I'd assume its mainly the engine and memory clock speed which is different between manufacturers.

The difference between those two cards is the higher clocked one is most likely better binned and has a better cooler. It can afford to overclock higher if it is better binned and with a better cooler it can still remain cool.

Right ok, assuming I get lucky, I could get the lower priced one then.

Could you apply this to other components were the only difference is the base clock speed, so you can just overclock it?

Most other cards are exactly like that. Some brands even have higher clocked cards (evga is one of these brands) that are simply better binned cards that are more capable of performing these overclocks.

You could get lucky and find a card that can outperform a more expensive one this way but chances are you won't.

Thanks for the help. On another note what graphics card would you suggest. As a suitable upgrade for my 560ti. I like to stick to the 2 year/series rule but I would go forsake that if it was cheap enough. I'm looking at max £250, though preferably not much more than £200.

Probably an nvidia 760 or amds r9 270. I would just look up either of these cards in google then add benchmark to the end, I haven't really looked at mid tier cards in a while so I don't really know which one is better but these two are basically at the same price point.