How to choose the best RF Connector for Antenna

The important issue is what connector is used on your test setup- signal generator, receiver, or a VNA. Impedance may be 50 Ohms, some cases need 75 Ohms, etc.
If your antenna is to be used with a high power, find a connector that can handle it. Operating frequency is also important.

Most test equipment now uses SMA connectors up to 18 GHz, k-connectors up to 40 GHz. There are N-connectors usable to 26 GHz, and many transitions available as needed. Better quality means a higher cost , too.

There are lots of things to consider.

* Coaxial or waveguide flange
* What it needs to mate to, as that is often defined for you.
* Frequency range.
* Power
* Cost
* Is passive intermodulation distortion an issue?
* Is it expected to have many connections/disconnections?
* Permissible return loss.
* Does it need to be water + dust proof, and if so to what level?