I use about 3,5 liters of fuel with both the P-160SX and AMT NL Olympus HP.
This give me 7 minutes of flight time and 9 minutes runtime.
One of the reason the AMT is more fuel efficient compared with the JetCat is because with the P-160SX I flew 90% full power all the time to give me decent speed, what the plane suits and to perform smooth aerobatic. With the AMT I can fly much more on partial power and therefore much more dynamic when fuel power is needed with a wider speed range.
The vertical is so much better and enjoyable!
I always thought as well "lighter is better" and this comes from my indoor F3P and 3D aerobatic past.
With bigger jets, a little more can be a advantage flying a smoother rock solid jet.
Take a look at the Skygate collection Hawk with less then 20 kilo's of weight. In my opion you really can see it is to light for its size.
Add 5 kilo's more and the jet performs so much better and realistic.
Anyway the 1,5 kilo more weight in the UL with the AMT was what "my" UL needed to be more rock solid in the air.
This is my personel preference and opinion and ofcourse everybody has there own.
But the statement bigger engines needs more fuel is not always true.