I think the HITEN is there since it's more spammable than the GAST. It probably won't matter much in the first few rounds which is more powerful than the two, since its magazine reload is faster than the GAST but I'm sticking with GAST if the purpose is to use it a little longer though.
I'm not sure about this, but HITEN and GAST had different sight types too.
I'm not sure about this, but HITEN and GAST had different sight types too.