I would ask /r/socialism because this seems more like a political question rather than a historical question, and we have a lot of Luxemburgists and Trotskyists there!

I'm not an expert on the two, but it seems to me that Trotskyism is much more closely aligned with Lenin, and became it's own philosophy in contrast with Stalin. Note that Luxemburg was critical of Lenin's Bolshevik party, and Trotsky was a part of it (though critical at times).