Haruno
Skadi :)
You're thinking about it the wrong way, you're essentially trying to compare latios with gliscor. They do completely different things. Considering I mostly play ubers I'll be speaking from an ubers PoV. You won't send a banette in to sweep or to wall anything, you send it in as a check to pretty much the entire tier. With only 2 mons that see any type of usage threatening it, banette has one hard defined role as a subprotect mon + the ultimate answer to xerneas. Banette is incapable of wallbreaking like mawile can, while mawile is incapable of being as big a stall breaker as banette can. Don't believe me? Here's some random replaysMawile has much better physical bulk, a ton of resistances and its just way stronger. Maxed MegaMawile is packing the equivelant of ~260 base attack. Not to mention a superior movepool and a cool pre-Mega ability.
http://pokemonshowdown.com/replay/pokebankubersbeta-58546880
http://pokemonshowdown.com/replay/pokebankubersbeta-58550835
http://pokemonshowdown.com/replay/pokebankubersbeta-58560216
http://pokemonshowdown.com/replay/pokebankubersbeta-58569256
Man wtf is a banette anyways. Fucking weak shit.
Anyways as you can see, banette doesn't or really it can't take advantage of that not so impressive 165 attack however it does have a hard defined role as a toxic staller. What seperates it from sableye? Well for one, it lacks recover but more importantly in exchange it has prankster destiny bond which is a more than fair trade off. The only two mons threatening banette in the slightest are mega/lucario with its bp and gira-o with shadow sneak. Meanwhile everything else is merciless as it cleans up lategame. Will banette be taking out whole teams singlehandedly? Of course not but it can definitely have a well defined role and excels at it.