There are tons of ways of boosting your + to hit in game (archery style, bless, etc), and given the design of the game is higher hit chance (so hits count more often), +10 seriously imbalances the game. Especially with Fighters.
Someone over at the official forums as also done the maths and proven it's generally always worth it using the -5/+10 option.
Having actually done the math myself, this just doesn't hold water in the absence of external bonuses. Yes, you can get bless and advantage. Melee can't use archery, of course.
At level 4 a non-feat GWF style fighter wielding a greatsword does more damage against every AC from 13-25 than the feat guy. If he's got +2 from bless it's better for the non -5/+10 guy for every AC from 16-25. Yay?
At level 8 when the feat guy has 20 Str and so does the non-feat guy non-feat guy does more damage from AC 18-27 and the feat guy only does 3-20% more damage from AC 17 on down to AC 13. Sure the feat vs. non-feat guy is better at higher levels. He had better be! You are taking a feat!!! And even then the damage bonuses are a modest 3 to a good 25% with the 25% against really low ACs. A level 4 fighter adding 2 to his strength gets better damage boosts than that. As a fighter you are likely better off boosting Strength at levels 4 and 6 and a feat that isn't better than boosting your stats isn't really a broken feat.
And I'm not particularly impressed with a lvl 17 fighter doing 80 damage a round. You can have a Rogue/Ranger with nothing but Hunter's Mark and Sentinel do 84 DPR with a 60% hit rate all day long every day and HM is a piddly 1st level spell. If he had advantage, too, he'd be at 105 DPR and that's not even an optimized build.
If you are a Champion, the GWF feat is sweet with its extra attack on critical. But you could just as easily take Polearm master and that's never worse versus any AC level. Oh, heck, just take both feats, right? You've got 7 ABIs!!!
The damage boost from Shield Mastery (assuming the DM lets you knock prone with shield and then attack) is greater than that for the -5/+10 feat and all your melee friends benefit, too!
Sharpshooter is quite good because of the hit boost although its effectiveness is mitigated for a Ranger using hunter's mark and colossus strike simply because each hit strikes harder than a fighter's so the +10 isn't as meaningful. You've already got +8 from HM and CS. For a fighter the feat rocks.
I'd rate every damage feat I can find in the book above the GWF one. At least I'd take them before I'd take a stat bump. Sentinel on a Rogue is sick! Hey, look! I get a second sneak attack opportunity. Yay! CE? Yay!!! extra attack with my hand crossbow, can fight in melee, and I can use a d10 ranged weapon with extra attack? Yay!
Except perhaps Dual Wielder. It's +1 damage going from a d6 to d8 and +1 AC. Stat boost is +1 damage and +1 hit.
