Superman is objectively more powerful, with even just his tactile telekinesis (super- strength) and heat vision outclass Homelanders by leagues. Even from a narrative standpoint, he HAS to win. He is the embodiment of hope and friendship, two concepts that The Boys' universe is simply not pessimistic enough to snuff out, seeing as how the titular Boys are still intact and themselves united in hope and friendship, however grudging.
Also, as soon as Homelander realized the fight was an even one, he'd get the f outta there, because he's just a coward and a bully. Superman would gladly give everything he has, including his life, to make sure Homelander was stopped.
Superman is the obvious answer for supporting and in competition of who would win. No matter how strong Homelander is, he is still a lab generated supe. However, his instability gives him a massive advantage over Superman.
Homelander is a terrifying creep