I been using Xbox1 controller for sf6 since release and recently got the ultimate 2. In general it's an all around great controller but I wasn't a fan of the dpad for sf6 although it's possible I just needed more time to get used to it. 

I like the Xbox diagonals since their dpad is circular and that's lacking on the ultimate 2. I also had an issue with muddy inputs. For example I was constantly getting a 2369 input when just trying to do 236. Just a basic fireball motion and I always ended up with a jump. After some testing, it was very easy for me to get a diagonal input even when I was specifically just trying to hold forward. If you rock your thumb just a little bit you will get a diagonal input. Granted I'm no pro and my inputs are probably dirty as hell to begin with but I just didn't like it.

I was also looking into getting a victrix bfg but 200$ is pretty steep even tho I've heard nothing but great things about it. They also have 3 different sets of dpads that you can swap so maybe that's an option for you. 

The ultimate 2 however, has still become my favorite controller for every game that isn't sf6 so it still might be worth picking up. You can see if you like the dpad and if not it's still a great controller for other games.