Racks are more economical, AP cages are stackable... but will cost more in the long run for sure (even still it's what I use/prefer)

If you are planning on housing different types of snakes, I would say that the cages are the better option seeing as each cage (or even each side of a divided cage can be kept at different temperatures/humidity levels. For example right now I have a Carpet python and a Dumeril's boa both in the same AP T8 (using the divider to separate them of course) each side has it's own heat tape/thermostat channel, and I can keep each side at its own humidity level...

but if you are planning on keeping large numbers of the same thing, a rack for each type would probably be your best bet.