Well it depends.
Different manufacturers get the designs of the card, and some make changes, etc which can affect performance sometimes.
For instance, some fit there own heatsink/fan which can affect overclocking performance if your interested in that, and also, affects noise of the card from the original model (quieter or louder depending, though keeps it cooler for overclockig potential, or just simply for the quietness for a quieter computer)
Others actually change the performance by overclocking it slightly from ATi's specs, and make some small changes to affect other parts which can differ slightly from the original design.
Though the ones you've listed with this card will not make many changes at all.
Plus of course with different manufacturers, you'll get different game bundles, etc, and accessories with the card.
But most of the time it is up to you, and you might want to note, that the last 2 links are the same card. It says ATi, but if you go further down, its a Sapphire ATi card, like the other one. (Still designed by ATi originally though, so drivers, etc are supported)
With these two makes, as you can see, you simply just get a different colour of board, and maybe different games/accessories depending if its a straight shop one, or one that just comes with the board and driver.
I'd personally go for Sapphire from experience from that list, but I've never tried PowerColour, so don't know, but I've heard they are good too.
I hope this helps