Thats the thing, already in the cult of razer😅They both use the same materials/finish, so it's really just a matter of size (although the Firefly claims "highly responsive tracking").
Honestly though, you're comparing RG Mousemats that both have a solid amount of "Razer tax" attached to them (ie you're paying for the brand more than anything else).
Unless you're already heavy into the Razer ecosystem, I can't help but feel there are rival/better products that would worth considering before either of these options.