Red Mango (on Rodrigues x Torre) opened just around the corner from Tartini (on Stevens Creek x De Anza), and while it has a much smaller selection of yogurt and toppings, it does have cute, soft, little mochi balls as an option! $3.95 for a small portion (you don't get to serve yourself as you would at the other two shops); the service is friendly, and the yogurt is a bit smoother than Tartini's. Tartini has a better fruit topping selection.
My teenager prefers Yogurtland (behind Elephant Bar on Stevens Creek) because it has chocolate (too sweet for me) and other sweeter flavors. It has the largest selection of yogurt flavors and toppings, and while it seems to be the yogurt of choice for the teen set, I found the quality comparable to RM and Tartini. It was fun doing the taste test, and they were all worth a visit.
20560 Town Center Lane, Cupertino, CA
19700 Stevens Creek Blvd, Cupertino, CA 95014