If you're only going to use one or the other, floor is better for the snake and is much easier to use. Also cheaper and safer. Unless it's for Diamonds, Bredli, maybe Murray Darlings and maybe SW Carpets, I wouldn't ever bother with spotlights/basking lamps/overhead heating. Diamonds are best kept cold for most of the year with basking lights, Bredli, Murray Darlings and SW Carpets don't need that sort of thing but do have a natural inclination to use it if it's offered. For all other types I definitely just wouldn't bother.
Carpet Pythons are among the most 'basking' of all pythons. Most pythons are tropical and will do best with floor heat only.