Worldwide there are and have been many Trotskyist parties since the 1930s but no Menshevik groups as far as I know. Initially there were more Menshevik intellectuals in exile from the Soviet Union than Trotskyists. What explains its' comparative lack of popularity?
I'm unsure if this qualifies for a top-level comment (can't think of a particular source), so mods delete if you so judge, but:
We were taught that after Stalin's atrocities became widely known about, Trotskyism was the only 'respectable' variety of Communism that Western Communists could claim to adhere to while disassociating themselves from Stalin's mass murder.
This held true until Mao came to power in China, when (up until the cultural revolution) Maoism became almost equally popular amongst Western Communists.
It is highly unlikely that self-described Stalinists would have been able to successfully infiltrate more moderate left-wing organisations like the British Labour party in the way that Trotskyists did.
Since Menshevism had no charismatic leaders etched into people's conciousness nor had ever been in power to demonstrate its beliefs in government, it would have been a bit too obscure to win converts amongst the radical left in Western Democracies. Trotsky, however, was a war hero of the original Red Army who had died a Martyr's death.
The bad ideas in Trotskyism inspire Western bourgeois ideology in ways that the bad ideas in Menshevism do not. Eternal revolution and achieving proletarian internationalism (like some Bodhisattva vow to not cross humanity into socialism until we all go together) are romantic and appealing to nationalist mythologies present in Western traditions, while arguments about vanguard parties vs. intermediary stages of state capitalist development or whether imperialist nations can be negotiated with as temporary allies are arcane minutiae.