Release date (though that's looking too likely given xbox series x is releasing in November but if Sony opt for a December release (which I don't see happening), it would give xbox a potentially significant headstart.
Stock (though Sony are calling for a pretty large release)
Price (I could see this being a factor)
Hardware issues (launch consoles often come with their own flaws, if the PS5 has any major issues, it might turn people off until it's fixed)
(i don't have a better way to describe this but we do know both Sony and Microsoft are holding back on info, I personally don't know what they could reveal that could push them up like Halo did but it's worth noting at least).