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.
Flanking is an optional rule in the D&D Dungeon Master's Guide that grants players advantage when their characters attack opposite sides of an enemy. This optional rule can enhance tactical aspects of your game. Understanding more about how this affects different characters can help you decide when to use flanking in your campaign. If you're a player who knows your DM employs the flanking rule, this may help you avoid some pitfalls.