Both, but I'm greedy and like to have everything
For a walkon you don't really need lots of pods - it depends on how much you shoot and the efficiently of your gun / the air you are carrying. Walkon games are probably around half an hour to an hour at a time, so you can restock
Unless you are giving out paint then you don't need to weigh yourself down with more than you can shoot
At an event such as a scenario with respawns, in game air fills etc you may carry more paint, but consider that against weighing yourself down and how far you have to go to replenish
A pod belt is simple and efficient (some, but more rarely now can hold a bottle if you go remote)
A tac vest lets you carry more than paint depending on configuration, and is either fixed or can be changed if it's Molle etc (and you're heading to more £)
If you're going to carry paint pods, radio, misc stuff such as chocolate, notepad pen (if you're involving in 'complex' scenarios), torch, dump pouch or 'prop' gathering bag then Molle allows you to configure what you want
Molle costs much more to setup, but if you chop & change then one Molle vest and lots of pouches cost less then multiple vests (possibly!)
You can get almost both in one with some 'yoke' style Pod belts / mini Molle rigs
Personal preference is key, how comfortable it is to you and how natural it is to draw a pod etc