I want to get a <whatever>, which manufacturer should I choose?
Well generally speaking there are a few ways at looking at this:
Since you're asking then odds are you wont notice the difference in any of the manufacturers ... so get the cheapest one!
Certain manufacturers tend to overclock their parts and so compared to the stock models, you will get a bit more performance out of them; the flipside is that you'll be paying a price premium. Some examples of such companies are ASUS, BFG, HIS, Sapphire and XFX. Not only will there be a difference in the performance, often there will be a thermal/acoustic difference as special aftermarket coolers are often used (see HIS/Sapphire for clear-as-day examples)
Certain manufacturers tend to have lower-than-average prices: some examples of such are eVGA, MSI, Powercolor and Sapphire. Sometimes there's a catch but sometimes (probably more often than not) you're just getting a better deal without any strings attatched
Some makers are generally known for doing really wild stuff with their cards: ASUS, eVGA, Gigabyte, HIS/Sapphire/Powercolor etc are some examples
But yeah, for the most part, it wont really matter all that much between makers.
ty all