Look like operating current: ~0.95(H38) vs ~1.15A (H44)...
Judge, because H38 IS 0.95A (i verified their exact ratings/parameters to find/assemble proper ballast for them, as i acquired fe such lamps) and the MV125W itself is rare for US and i've seen it only in "European lamps" sections, so i guess ANSI assigned the H44 for them and this is 1.15A lamp.
