We've done music with mummy, Jo Jingles, tiny talk (a bit different but still all singing) and a small local group run by a church.
Music with mummy was least 'commercialised' / branded. I like that. Also the 'themes' and 'bring things in'. Teacher was good. material all quite old-fashioned, lots of 'new' songs, not much in the way of 'gimmics', listening slot with music to listen to, random instruments rather than all get the same thing.
Jo Jingles was heavily branded and structured. They all have the same instruments at the same time. My DSs both love it (ages 1 and 3). The teacher is fab, so I like it too. There's a 'theory' slot when she talks about pitch, loud / quiet etc. All kids have the same instrument at the same time, and there are about 6+ different instruments, which are introduced well. At least one gimmic / toy in each session, which is a big hit with the kids. Most of her classes are far too big, though.
Tiny talk: structured and branded. teacher not v good. Didn't enjoy. I hated sitting on chairs with baby on my lap - I prefer sitting on the floor. Good play and drink time afterwards. Only for kids under 2yrs though.
Local group - friendly, had play-and-drink time, pretty unstructured and chaotic.
IME, the basics are much of a muchness (you go with child, songs are sung, instruments shaken, you go home) the biggest things are the teacher (current JJ teacher gets DS1 to do stuff no-one else has ever got him to do), the class size, and play-and-drink-time (currently a turn-off for us, but can be v important if you want to meet people.
There's also Monkey Music which is widely franchised.