>>58005434
Maximum skill edges out over BFS. Of course a small portion of Berry Burst is reliant on your other team members' types, so a skill-focused one is swayed more by that.
I did a separate comparison and at the absolute maximum: BFS + Helping Speed M + Skill Trigger M, Skill up nature beats Speed up nature until Helping Bonus maxes out their speed.

I suppose what's more interesting is that BFS Sceptile can almost beat a BFS Meganium in raw berry production (not counting its skill).