Both are bifl.

And imo both have their place.

I think nylon is going to be better if your destination involves being outside and adventuring.

Leather is better if you're destination is for work or if you need to look classy.

I also disagree with the idea that leather requires more maintenance, it's just going to look shitty and defeats what I consider to be it's purpose if it gets stained. That can be cool, and give a used look, but then you're potentially specializing even more.