>>15330604Choice Band Scizor is arguably better for the standard Bullet Punch + U-turn + Pursuit + Superpower set. However, Mega-Scizor gives you bulk and power that would be useful towards a SD set, that is:
Swords Dance
Bug Bite
Bullet Punch
Superpower/Roost
Really not much to be said here. Swords Dance up if you ever get the opportunity to meet a scarf user face-to-face. Bug Bite becomes better than X-Scissor after the Technician boost, and also has a secondary effect that will be useful once in a blue moon. Bullet Punch is your primary move, which does heavy damage against those who don't resist it and of course is priority. Roost helps you set up easier, but Superpower hits those steel types very well, especially Heatran and Ferrothorn, although it has some obvious drawbacks.
Run it Adamant with all your EVs in Attack and HP. Optionally, you can run 28 speed EVs to outspeed bulky Heatran with 8 speed EVs (some people run 8 speed EVs just for the edge in Pokemon like Heatran), but only if you run Superpower otherwise it's useless. Make sure to note that mega speed is not accounted for the turn you mega-evolve.