I havent seen yet a good qulity rep leather strap. Thats it. If leather you'll need to source a custom one, there are plenty of good strapsmiths.
Rubber is a different issue: some of them are gen like, watch the advices ie. 104, etc, watch the advices of Ale.
The preference is determined by the way you'll wear it.
I'd go for a great exotic one from Rob Montana.
Good luck.