At both airfields, one can find AVGAS 100LL, which is very convenient.
In Genk, billing is based upon clock time and in Luxembourg, billing is based upon engine time which is different. My experience is that when I have been flying let’s say one hour, that the Luxembourg bill is often not 1,0 but rather 0,9 or sometimes even 0,8. On the other hand, in Luxembourg, which is an international airfield, one needs to taxi longer before taking off and one needs to orbit 360° circles in downwind, because of traffic which has priority. All by all, I think you therefore can compare both rates for local flights at least
A Cessna 172 (N-series) costs in Genk 150€ per hour and in Luxembourg 164€.
For a Cessna 172SP with glass cockpit, the price per hour is in Genk 180€ and in Luxembourg 196,5.
Some other rates:
– C182Q costs 261,7€ per hour in Luxembourg
– C182RG costs 306€ per hour in Luxembourg
– Mooney costs 210€ per hour in Genk
– C152 costs 120€ per hour in Genk