A specialist is the right hire once you know exactly what you need specialized help with. Hired before that point, a specialist doesn't just cost more, they quietly narrow your options at the exact moment you need them widest open.
How this plays out
A specialist naturally sees problems through their specialty's lens, that's what makes them valuable once the direction is set. Before the direction is set, that same lens becomes a bias. A performance specialist hired early tends to find performance problems to solve. A growth specialist hired early tends to find growth levers to pull. Neither is wrong exactly, but the direction gets shaped by who's in the room, not by what the business actually needs most right now.
What a generalist does differently in that window
Sees the same situation without a specialty's gravitational pull toward one category of answer. Can hold "maybe this isn't a performance problem at all, maybe it's a positioning problem" as a live option, because there's no professional incentive pushing the read one direction.
When to make the switch
Once the actual bottleneck is identified with real confidence, not a guess, a specialist becomes the better hire, because now their depth is being pointed at a well-defined problem instead of shaping which problem gets picked. Depth is an asset once direction is set, and a liability before it is.
The practical test
Ask: do we know specifically what kind of expert we need, or are we hoping an expert will tell us what kind of problem we have. The first case, specialist. The second case, that's exactly the situation a specialist hire tends to quietly distort.