I picked one simple metric because it was easy to calculate. In my scenario B is also better at everything outside of combat as well, not to mention just something as simple as having a far better initiative.
It's funny, in a way: discussions like this are the closing of a circle that began in the early TSR days. To explain:
In, say, 1e all members of a given class are mechanically close to identical. Class features come online in a regular predictable fashion as the character levels up, with no choice involved; with the only real variable being what spells an arcane caster might have acquired. And, in various (sometimes unintentional!) ways the classes are surprisingly well balanced - or were until UA came along - in the long term, i.e. over a 1-10-ish level span; and short-term imbalances were obvious enough that players could work around them.
For some of us, this is just fine. As player I can take two mechanically-identical characters and have them come across as night-and-day different (and, to the eye test, highly imbalanced!) in play, to the point where you'd never know that under the hood they're exactly the same. I don't need mechanics to differentiate my characters from each other, and the resulting simplicity in char-gen is a wonderful and very desirable side effect.
The flip side of mechanical sameness in classes in 1e, however, was the randomness inherent in rolling for stats and hit points (along with a few other character-build elements); you never knew what you were going to get to work with.
For others, though, mechanical sameness within each class wasn't good enough; and "others" here clearly included the designers of every edition since, who have bent over backward to expand the game-mechanics of classes along with adding reams of class-agnostic feats and abilities, such that any difference in character is or can be mechanically reflected. Add to this the vast expansion in PC-playable species and there's never been so many options for character building. The cost, however, is that character generation has become almost its own little solo mini-game and a tedious exercise, and inter-character balance at the design level becomes much more difficult (that is to say, nigh-impossible) because there's just too many moving parts.
Add to this a much lower focus on long-term balance in favour of a focus on short-term or even immediate balance (IMO a fool's errand at best), and you get 5e.
And to counter this, some want to harshly rein in the randomness of rolling for stats, hit points, etc. in order to - in theory - enforce balance from a different direction.
In effect, all this does is replace cookie-cutter classes with cookie-cutter stats. Cookie-cutter classes, however, are IMO far easier for a player to paper over with good roleplay and characterization.