[quote=Rin]
Only two, yes. They didn't want to upgrade it to three after Dende told them that doing so would lead to them having the same drawbacks as the Namekian Dragonballs (ie. can only bring back one person at a time, etc.).
[/quote]

Which were then changed to work with as many people as needed in the buu saga. (the namekian dragon balls I mean) Makes sense that the namekian ones are stronger though tbh, they are the original.