I'm in the same boat as you...evolved two Scisors and they both got FC/IH too.
Bug moves are strong vs. Grass, Psychic and Dark whereas Steel moves are good vs. Ice, Rock and Fairy. Meanwhile Steel is resisted by Fire, Water, Electric and Steel and Bug is not effective vs. Fire, Fight, Poison, Flight, Ghost, Steel, Fairy.
I'm assuming Night Slash is out of question with very low dps. So the other possible movesets are pure Bug FC/XS, pure Iron with BP/IH and BP/XS.
Looking at the strength a FC/XS Scisor would destroy Exeggutors and be good against Tyranitar and Espeon, while being resisted by Dragonite and Gyarados. A BP/IH Scisor is good against Rhydon and Golem and useless vs. Vaporeon. That for me eleminates BP/IH because you will go through Rhydon and Golem with Vaporeon. BP/XS is a little more complicated but I would say that it is inferior to FC/IH because while BP has more dps than FC you build up energy slower to unleash a weaker charge move. So with FC/IH you build energy very fast and can unleash the stronger IH more often.
So that leaves FC/XS vs. FC/IH. I will exclude Espeon of the equation because of her weak endurance as a defender. For a matchup with Exeggutor you certainly want the double bug move but this of course depends on if Exeggutor is still a relevant defender in your region. Regarding Tyranitar for me FC/IH is the prefered choice. Steel and Bug both deal effective damage, FC builds energy faster and has a lower cooldown that makes it easier to dodge. You will absolutely have to dodge the Fire Blast in case someone powers up a Tyranitar with FB. Of course Machamp will always be the better attacker into Tyranitar but I think in general the FC/IH moveset is a good general attacker who is still good vs. Exeggutor and a nice alternative against Tyranitar which from the numbers should be the moveset with the most dmg output (3 dps loss vs. 4 eps gain for FC vs. BP to unleash a charge move with 5 dps more)
Maybe there is someone with the exact calculation?
