We're comparing the Martial Adept feat and the Magic Initiate feat. While the effect of linear fighters vs. quadratic wizards most often manifests in class design (mostly due to spell access), there’s an interesting reflection of this design in the 5e feats, which we expect to be balanced against each other.
We're going to make the adventuring day agnostic as to character class. That way, everyone's going to be on a level playing field, regardless of how many encounters you run. How do we do this with linear fighters and quadratic wizards? It's simple. We kill the short rest.