I have the same decision to make too. But i will choose KTS for the following reasons:
1. KTS teaches Chinese in Putonghua
2. KTS class size is smaller (35 KTS vs. GH 45)
3. GH classes start at 7:30am (my GH school bus departs at 6:35am). This is too early for a 6 years old. My KTS school bus departs at 7:20am.