Even more than Hitler, it just feels strange to have any variant of Stalin without that moustache. Even gender-bent, to be Stalin is to have Stalin's moustache.
Actually, no, the artist did their research--Stalin famously declined to wear the more distinct Marshal's dress parade cap (sort of the same way he regretted and eventually dismissed with the distinctions of 'Generalissimo of the USSR', and generally requested people refer to him as Marshal). Hence, why very photographs have him wearing the Marshal's cap (or any cap at all). He wasn't a fan of military decorations (generally why his public appearance was so plain).
Plus, the one on the right has very clearly Marshal's rank boards (which Stalin did wear, presumably because he liked the uniform) and a pipe (Zhukov is almost never portrayed with a pipe, it's very much something associated with Stalin himself). Zhukov is definitely the one on the left.
