Same card, different manufacturers

I'm in the market for either a 560 gtx or a 560 gtx ti. Now, I find that there is a great deal of price variability from manufacturer to manufacturer. Now, part of that is explained by:

- factory overclocking
- different editions of the cards (i.e. 1 gb vs 2 gb, the ti with 384 shaders vs 448)
- improved cooling

However, if two cards are identical in all of the above attributes, but have different manufacturers, they will have the same performance, right?

In theory yes, my cards were the cheapest ones available when I bought them and yet they chuck out the same framerates as cards that were much more expensive and they seem to run at about the same temps.

It should be, except some graphics card manufacturers support aren't that good, or have low warranty covers. Also some people have said to avoid not-known manufacturers because they tend to have more failure rates, but I can't confirm this.
Just only said by some.