I find Co2 stuff is like buying a car, really depends what you want out of it, and what your budget is.
are you looking at running one co2 setup for two tanks? you'll need separate needle valves and bubble counters for each tank, either all attached through a manifold, or run them inline.
If you are planning on buying two units, and running two tanks, IMHO, that's a waste of money, Dual stage regulators, also waste of money, I like fabco-NV55 needle valves, get any of their setup's with it, and you'll be fine.
Paintball has its place, I'm setting up a new tank with a paintball setup with the Atomic Paintball Co2 regulator v1 that I modified to my needs. I had space constraints and solenoid needs of low voltage.
Search around the threads for co2 setup, and you'll find a ton of info, stick to what people actually use, and stay away from stuff you find at Home Depot or Lowes.
Keep in mind I've never ran this setup yet, but here are my recommendations.
For paintball tanks, small and super compact:
20-24oz bottle from amazon is like $20 and $3.50 to refill at sports authority.
For regular co2 tanks:
or for a little more money for a nicer regulator:
or you could build your own for cheaper, with say a victor co2 regulator, Clippard EV Mouse solenoid, and Swagelok metering valve for maybe about the same money.