+1 To me Stuart is just the "I don't want to deal with LVs so I'm going to overkill them with light tank" unit. The fuel premium you spend on it is just a risk/reward on how much map control you wrestle back as a result of forcing your opponent(s) to be more conservative with their LVs. If you don't get more control than you otherwise would w/o Stuart then it's not worth it.
Don't know stats offhand but I think Stuart and Greyhound main gun are roughly the same AI potential wise. Greyhound's DPS superiority is all pintle and cheeky canister rounds. So in that way Stuart isn't terrible but certainly not worth it if it isn't primarily being used to reign in LVs. IMO
But USF isn't supposed to be the lv faction? To me the premium lv in this game is the puma, not the stuart.