My admittedly limited experience has been this : if you're expecting Western tour standards, be prepared to pay western prices.

I did a private tour from 成都 to 九寨沟 黄龙 with one of those larger Chinese tour companies offering private tours to western tourists, even though we're both chinese with foreign passeports. It turned out great, the company was responsive to last minute changes (we finished earlier than anticipated the last day, they swapped our train tickets no problems at all).

The risk with the local small tour companies, would be the quality of the lodging, transports, accréditations, and language if you don't speak/read the local language. Also, I didn't want an experience with the cliché shopping tours.