YUURAM OR WOLYUU?
What is the difference? Well if you are familiar with the terms Seme and Uke then you might have some idea just from that.
Seme is the more manly, dominance one. While Uke is the more girly and submissive one. The reason behind the names is with Yuuram you are calling Yuuri the Seme and Wolfram the Uke and with Wolyuu it is the opposite. It's all based on personal opinion.
My own opinion is, I wouldn't care as long as they are together. XD
I think the reasons for the different opinions of this couple being the Seme and Uke is because the novels seem to be a lot different from the anime.
In the novels Wolfram is said to be a lot more manly, but hides it a little more around Yuuri because he knows Yuuri doesn't want to be with a guy. This is all from what I have heard though. I can't prove this or say it's my own opinion because I have never read the novels. I don't really doubt all this though.
So if you read a fanfic that says either Yuuram or Wolyuu there is a difference! But who cares right? It's still them together? hehe XD