Well the G2 and G10 are pretty different. They're about as different as you can get for 109s. G10 has one of the top 5 best climb rates in the game (much more powerful engine) but is also much heavier and turns worse than the G2.
The G2 is one of the best 109s (I consider F4/G2 to be nearly identical) for turning. It is much lighter and far more agile, in that you can actually turnfight with it. That being said, gondolas really screw up its ability to turn fight, so don't take them.
Which leads me to guns. It does not have a good armament. 1x20mm with 150/200 rounds (depending on what you pick) does not last long. Save your ammo. Get in close. Kill. Get out.
Flying a 109G2 will teach you better gunnery or it will kill you
