They use the standard CO2 cylinders, not the soda stream quick connect ones. I got an omnifizz to replace my soda stream and have been really happy with it. It doesn't need electricity (our soda stream needed to be plugged in, not sure if they have powerless models), and the way the cap works lets you carbonate pretty much anything without it spilling out when you open it.
I would say it depends on where you are, as some brands are not available in every country. IMO start backwards and find out which places near you offer canister refills or generic exchanges, and pick a compatible make. There's also adapters that will let you plug in generic CO2 tanks into soda makers. Again, find local distributors of clean CO2, and you'll have bigger refills for a fraction of the cost.