The only difference really between the 980's are the brands that produce them. Each have their own ideas on cooler design and color schemes. But ultimately, they are all pretty much the same. NVidia does not allow any company to modifiy their architecture beyond a certain point, so they all end up being roughly the same. Find one that looks good to you and go with it. Personally I prefer EVGA but I hear great things about MSI, Gigabyte, ASUS, Zotac (in no particular order).
If your looking to do gaming in 1080p though @ max settings. You'll be better off with the R9 390 or the 970. The reference GTX 980 isn't all that good for the money and the 980ti is overkill for most people.