The biggest difference between Sodastream models is in the method of carbonation. The basic models require pushing the button until the desired level of carbonation is reached.
The more advanced models, however, will have an automated process of carbonation that will take the guesswork out of home carbonation.
No matter which model you choose, the biggest ongoing cost will be replacing empty canisters.
Fun fact 1: that’s cheaper than you can get at the shops.
Fun fact 2: The biggest fall from grace in the animal kingdom? Leeches, probably.