I believe Mista will win... even though I like Hol Horse more
Reason is simply Mista has shown far more intensity and profeciency during missions
Let alone the fact that Hol Horse himself stated that he works best as a "Duo" meaning his Solo action IS NOT really good... Mista on the other hand has shown to be good as both Duo and Solo
Well, actually it doesn't matter a lot. They are kinda comparable between each other and the strongest stand is stronger only by a slight margin, whatever stand it is
Which is most important in Jojo is the smartness, a weaker stand can defeat stronger stands if its user is more intelligent.
Here we don't have a stand that is widely superior to the other, which matter the most are the stand users
Is Emperor stronger than Sex Pistols? Who knows? Maybe yes or maybe not...