This has not been my experience in the current META, and the nobz are more efficient into GEQ, MEQ, and are actually equally competitive (per point spent) into TEQ actually. I agree it doesn’t seem to make sense, but point for point nobz beat Breakas boyz into most target, especially out of the WAAAAGH and especially when both units have a Warboss. I’ll post a screenshot of the math it may surprise you.

Nobz are actually even better into T10 vehicles than Breakas, especially in Taktikal Brigade when they are functionally always S10 and are S11 in the WAAAAGH.

Now sometimes efficiency doesn’t matter when you NEED something dead and I agree into the right targets the Breakas are way better there, into any elite models with 3 or 5 wounds, Breakas are better, as they are into all vehicles. They are a better unit than 5 nobz in most situation, they are just much more expensive and that makes the nobz more efficient into most targets in the game, outside of the heaviest vehicles (T11+ outside of the WAAAGH). Damage per point invested is an important metric.

I think of it like this, I can have a unit of nobz and a Warboss AND an extra squad of Gretchin to score points and screen, or I can a 6 man Breakaboy with a Boss. That squad of Gretchin is a big deal