every company that build cards has a very specific way of bulding there cards so you cant really say which company is better because the every company offers diffrent coolers.
for starter level the company doesnt matter as in quality but its more important to see who offers more warranty and who has better costumer support, all of the cards start in refrence cooler. same heat pipe same design same fan only diffrent sticker on the toop of the color (eye for gigabyte, sword for HIS,simple asus sticker for asus,evga has like rough metarial and galaxy has a big G on it) but they are all the same and how cool and how far you can overclock them is a matter of luck.
after that point you go into the more special cooler that offers better heatpipes ,bigger and buffier coolers but again all of the cards are very close performance wise and you should only be concerned about warranty and price.
when you reach the enthusiast level now there's a diffrence between companys. if its ASUS DirectCU II cooling which offers a massive cooler and quiet operation,Sapphire's Dual fan and 5 copper heat pipes that offers a better cooling then stock but not as good as the direct CU or MSI's twin frozr cooling but it has a smaller price tag so it is a good bargin, XFX double dissipation cooler which is magnificent and really beatifull and on top of all offers amazing cooling and a good price tag or MSI twin Frozr III or Lightning which again offers great design with silent operation and much lower tempeture. and the list goes on to Galaxy,zotac,sparkle,inno3d,Connect3D and so on, every one has a an extended cooler but on each module the cooler operates diffrently so on each card a diffrent cooler is the better choice. which is the best you ask? my personal opinion is either MSI Twin Frozr III or XFX Double Dissipation cooler, but those are my personal choice and i like those cooler because im really fond of XFX, something about them is tempting for me
sorry for the long message