It really depends how you use your case, are you a rough user? How long do you intend to use the case for, 3years, 5years, 10years?
Vinyls are getting more and more durable, I've seen their progress and cars(lower end) have been using alot of that for that seats so that accounts for something.
With that said, leather definitely wears better, generally more durable and can withstand weather better.
Vinyl will last long only if it doesn't "move" or fold much, if it has to succumb to constant folding and twisting then it's no match for a leather.