The larger wing area should make it handle easier than the Su-25T, so not surprised of that.
But it also should make it easier to go higher, atm Service ceiling in game is 10000m ( about 32000 feet) at mach 0.75, according to encyclopedia.
But after the hypoxia problem was fixed in 1.106, and I could try it up there, it only get to mach 0.59.
Also when i read wiki http://en.wikipedia.org/wiki/Fairchild_Republic_A-10_Thunderbolt_II, where it states Max ceiling 45000 feet, it seems that the A-10C is underpowered at high altitude.