To OP and most of the other posters : GWM and SS are NOT the uber feats because CONTEXT and you deal no damage if you MISS.
I mostly agree... People tend to overrate the -5/+10 feats by failing to make apples-to-apples comparisons. At worst, they ignore the -5 part completely. One step above that they hand wave the -5 by saying that you can simply "offset" it (with advantage, or with archery style, etc.), failing to also give advantage or archery style to the character not using the -5/+10. Or they actually model the to-hit chance making some assumptions but don't account for the opportunity cost of not raising your attack stat (once it's maxed out, the opportunity cost in terms of damage is typically less, but apart from fighters that's usually level 12, when most campaigns are over or nearly so --- yes, there's variant human, but you typically don't want to take these feats until you have XBE or PAM already, since XBE and PAM are bigger boosts to damage in typical cases, and so by the time you're considering it you really are foregoing an ASI).
Taken in isolation, the -5/+10 option is, on its own, a net damage
loss against the most common ACs, compared to raising your attack stat (SS fares better than GWM in this case, due to archery style shifting the window of the most common base to-hit chances, but even then the ASI is better against anything with above average AC).
Even having reliable advantage doesn't change the picture
all that much --- it shifts the AC window where -5/+10 is a net winner, but the difference in average damage per attack is still relatively small at common ACs (again, SS would fare better, but it is also harder to get reliable advantage at range, since the easiest option for GWM --- Reckless Attack --- doesn't work).
You can get more out of the -5/+10 option when you combine it with "use-on-near-miss" mechanics like Precision Attack, Lucky, or Bardic Inspiration. Especially Precision Attack, since it doesn't cost yet another ASI like Lucky, and you can use it much more flexibly than Bardic Inspiration. Of course, since a character without GWM can also use Precision Attack, even that synergy mostly just shifts the AC window where you want to use -5/+10, so you're more likely to be in the good range, but you're still not necessarily gaining a
ton of damage on average per attack (though on a fighter who also has XBE or PAM who is making a lot of attacks, it can be a decent chunk of overall DPR).