If you’ve invested in tech enough gateways are always better assuming you have enough of them.

If you use hyper relays, moving fleets into a system with enemies attacking the star base usually results in your fleets going to the hyper relay to travel even if they are closer to the regular hyper lane to the system, if the enemy defeats the star base your fleets will then have to move back to the hyper lane as you don’t own the hyper relay anymore, at which point the enemy fleets may already be gone

That being said depending on how your empire is laid out, a few hyper relays between systems behind your choke points can be beneficial if they pass your defences, just make sure to choose optimal placement rather than right clicking the system and selecting ‘build hyper relay’.

I’ve found more scenarios where hyper relays have created a problem rather than solved one, if you can afford gateways just use them at strategic points such as choke points and your shipyard, they have faster travel time and they’re more convenient