Why does microwave test equipment use N connectors?
Two Reasons: Pout and S11.

N connectors have a large surface contact area for >1A power levels or >10dB and large diameter means better "potential return loss over a wide GHz range is possible with machining tolerances of 0.1% affecting this.

However SMA is more common for low power apps but quality varies with undocumented suppliers. (greatly and not gauranteed)

But never try to pump >>1 Amp thru 1u" flash gold plated SMA connector (crap...