It's that christmas-shopping time of year, and I'm looking to get my parents a soda maker to complement their sparkling water obsession. Can anyone recommend one brand or style of product over the others? (ie the siphon style versus the Soda Stream bottle+carbonator, any other brands or styles, etc) I'd be interested in hearing the pros and cons of each (time delay? cost of CO2 cartridges?) as well as if there are different capabilities. Thanks!