I’d say both Stone Soup” and “Tina’s Groove” are “character driven” rather than “gag driven”, but “Soup” is of course a “family” strip (as is “FB/FW”), which means it’s going to have a somewhat different dynamic than a “workplace” strip like “Groove” (or, say, “Dilbert”). In the same sense, a “family” sitcom like “Roseanne” will have a different dynamic than a “workplace” sitcom like “Cheers” (to name two of my favorites in THAT medium).
It’s true that I “care about” Jan Eliot’s characters more than Rina Piccolo’s. They may not be as immediately distinguishable in personality as Tina’s gang, but their personalities are well defined (if more subtly). A line or action by Wally would not work if it were given to Phil, Val and Joan are quite different despite being sisters, but it takes some time to figure out who they are. Continued reading, and emotional involvement, are rewarded. Some strips are understandable and funny (or not) if you only see them once a month. Some strips take time to become familiar with.
Ultimately, though, I think I’d enjoy “Tina’s Groove” more if it were just, well, funnier.