Ukraine

Planes would be very important for air support. It is mostly why the counter-offensive is so slow. Russia fields planes and helicopters to bomb any armored thing that goes beyond anti-air defense coverage.

As far as I understand, russian planes have better sensors than Ukrainian ones, or there's not enough difference and trading would be advantageous to Russia because they have more planes. With f16, they would hopefully have better range than Russian planes (if they get the missiles for that at least, missiles that go with the electronic systems and may not be compatible with soviet planes).

Also, as far as I know, Ukrainian bombers are bombing at full capacity already (jdam and stormshadow among other things, I've heard they have like 4 planes able to launch stormshadows). More capable planes would increase their capacity.