Hi, I was discussion this a bit on Pokemon Showdown in the OU discussion thread. This is a broader analysis wide question but is significant enough that it warrants discussion.
There needs to be a more mathematical approach to discussion STAB moves that have alternatives. The biggest culprits being Surf vs. Hydro Pump, Fire Blast vs. Flamethrower, and the god-awful Hurricane vs. Air Slash.
Bottom line: accuracy must be approached mathematically and considered in all analysis. PP is also another concern. Let's start with the first example:
For the widely used SPECS Greninja set, Surf is mathematically better than Hydro Pump. In fact, Surf should be the preferred move on all water sweepers in Sun Moon because it is the better move:
Surf (90 BP) * STAB (1.5) * Accuracy (1) = 135 Effective BP
Hydro Pump (110 BP) * STAB (1.5) * Accuracy (0.8) = 132 Effective BP
Due to the commutative property of multiplication, it won't matter how many additional weather or item multipliers you add to this calculation. Surf will always out damage Hydro Pump, the only exception being Z-Move sets. The reason these calculations are important are because math determines your long term expected damage output. For every game Hydro Pump nails you that crucial OHKO or 2HKO that Surf wouldn't, it will lose you more by missing at an inopportune time. The longer one plays pokemon, the closer results will get to that statistical expectation.
For Fire Blast vs. Flamethrower, Fire Blast's small bump in accuracy over Hydro Pump makes it marginally better than Flamethrower. This means that Fire pokemon sets the two should be slashed, with preference given to PP considerations (sets with Roost should have Flamethrower, sweepers should have Fire Blast).
Lastly, Hurricane on Tornadus-T is egregious and must be addressed. Like discussed above, Air Slash is mathematically better than Hurricane on all sets except Flyinium Z, with Hurricane deserving merit if the Tornadus-T is on a Rain Team or a team weak to opposing Rain Teams. The math on that is as follows:
Air Slash (75 BP) * STAB (1.5) * Accuracy (0.95) * 30% Opponent not moving due to Flinch (1.3) = 139 Effective BP
Hurricane (110 BP) * STAB (1.5) * Accuracy (0.7) * 30% Confusion / 50% not moving due to Confusion (1.15) = 133 Effective BP
This is not to mention the fact that sometimes Torn-T as a pivot may need to just hit a weak opponent and shoudn't have to rely on gambling to do so. Again, the concept here is that if you use both moves thousands of times, Air Slash will be more successful, thus winning you more games.