I can't say anything about "looking better". I own (only) a PS4. My brother has X One. I've noticed no visual difference between any of the games we both have respectively. However...
Function wise, I'd say X Box.
The Mod thing, imo, for PS4, is still very much in the air. If I had a dollar for every time PS said something was "coming" I could buy every one of you a Pip Boy ! I honestly don't think it'll happen. Bethesda wants it to happen, no doubt, but I want my neighbor to paint his water stained puke orange house too.. Seriously it's gross. He's content with it though.
Then there's the management. Save files, particularly. I know for every other Beth game I've had many saves. Sure it'll be the same here. Just looking at them is a chore on PS and I'm already stressed out about how much time I'm gonna spend shuffling them around between HDD, USB, and cloud. The latter two having no info on how much space is being used. (Whoever can tell me how to find out how much space I have on m y PS cloud, will be my hero. There's gotta be a way...?)
There's a few other things, like no way of knowing if there's a disk in my system, but I felt those two are the most universal.