I love talonflame so that should answer your question:). I'd use it for the 5seconds it would be allowed in ou. Then it can go keep megamama/megakfc company.
Also, to keep this post relevant, do people use talonflame with megapinsir on the same team? I want to but that insane sr weakness scares me...
What does one hit that the other doesn't? Between the two you really don't get a huge amount of coverage, and they both overlap big on Flying-type priority. Talonflame has only Flare Blitz and maybe U-Turn for coverage, whereas Pinsir will probably run one non-flying move alongside Quick Attack and Return, and that move will probably be Earthquake. It's not even so much the Stealth Rock problem (though that
is a problem,) as it is the problem of them covering and being covered by many of the same threats. You're gonna have a bad time if you can't keep SR off the field, but both M-Pinsir and Talonflame will have problems with things like Rotom-W, Cresselia, Hippowdon, Tyranitar, and others. Basically, they don't get the coverage to take care of each other's weaknesses and they have problems with the same Pokemon that resist their moves or are otherwise too bulky to care.
Theoretically it could kind of work in the same vein as the Salamence/Rayquaza combination of DPP Ubers, wherein you soften the counters for the duo with one and go to town with the other, but this strikes me as a bad idea because this team-up has far more viable counters than Salamence/Rayquaza. You also have to deal with Team Preview, and any player worth their salt will realize right off the bat that you have a huge SR weakness.
So, there might be some reason to use the two together that I'm missing, but from what I can tell they don't really help each other out very much.