bro, Fisheye and a normal UWA are 2 different type of lens. If you are unsure what to get, I suggest renting first and see if you liked it. Like other seniors have mentioned, FE is not for every shot, thou it does gives you creative/nice pictures at times, but not all the time.
If you just want it wide, get a UWA, if you want a curvilinear effect, get FE. If none of these matter, I suggest you either dump it on a UWA or hold your $ till you know what you want.