We've been doing Music Together for almost 3 years now and our boys love it. It's really nurtured a love of music for them. It's nice that all the ages are mixed so families can all attend the class together. The downside though is at the age of 3, our oldest is the oldest in the class and doesn't seem to benefit from it as much (and can get a little bored) while the younger kids love having him around to model. We've also found that finding a good teacher makes all the difference- we've been going to the same teacher for 3 years and the boys practically worship him. The songs have always been seasonally topical which is nice, especially if you practice Waldorf at home. In our classes, there's always a free dance where the kids wave around playsilks

.
I'm not familiar with Kindermusik, though there is a program here. I looked at the site and a big red flag went up for me when it made the claim about promoting early literacy and math skills. I guess I just want my boys to have a fun place to go to get their "groove" on

. I also think preference/popularity between the two programs could vary city by city.
Will either program let you "test" a class before committing?