I think they're both some sort of decarbonizing agents.
I've avoided Sea Foam stuff, as it has a "fixes everything from dirty injectors to lubing fuel pumps to spaying the dog" kind of advertising campaign, which makes me think it's snake oil (despite the widespread use and numerous user testimonials.)
Ring Free is pretty simple to use - add the correct amount before fueling (to make sure it gets mixed in by the added fuel), and you're good to go. Don't know if it does any good or not, though. I used it fairly religiously when my motor was new, but haven't in the past, oh, four years or so. No difference that I can tell.