The UAT came about in the early days when causes of intermittent flameouts were not certain, the header/bubble trap gave more reliability and was so adopted as the norm.
Modern turbines and ECU's are much better and even if the odd bubble does appear it will not always make them stop.

Air bubbles get blamed alot, the pump, fuel valve, plus all those and other connections at ECU can cause it to stop suddenly, do a test while the turbine is running, pull the fuel valve plug out of the ECU and it will stop instantly, with guys having to add extensions to this lead, it is one unlooked at area, that a poor connection can cause more bother than any air bubble.
I have fitted new RJ12 plugs to the black telephone type lead used on Jetcats because of damaged pins, a bad connection here will also cause a turbine to stop intermittently.

My Old Boomerang has a BVM UAT and it always has air in the top corner, now I only use homemade centre pickup tanks which never have any air in it, so which is better?

From my view there is more benefit of having a header tank to provide a constant fuel source (as the heli guys do) than being fitted purely for use as an air trap.

Many have proven that a felt, orbit or similar clunks work well with no additional tank, so if it is proven to work and you have no room for a header tank then why not use this system.