It's pretty much a case of you get what you pay for. Wolf is generally cheaper but they are more approximations. You're not going to want to use them if you are doing a concours resto. But one real advantage is that you can talk to Allen and I have found him to be reasonable. He has made panels that no one else makes and you can send him a section and he'll reproduce it.
I am not looking at a concours restoration but a car that is rust free and one that I will enjoy driving without breaking the bank. If I spend too much money with the idea that I will sell it one day, I would be too afraid to drive it
The usual UK vendors have excellent quality sheet metal pieces and you'd be surprised on their speed of delivery and the relatively inexpensive costs. I've used them and never had a problem.
Wolfe's okay if you have a rust bucket that needs to get through some mandated certification process to get the poor car back on the road and be legal, but I think you'd be better off paying a little extra and get a good quality product to begin your repairs with.