This is a dilemma. Every site that offers reviews claims "We're 100% honest!" In reality, most of them will quickly remove (or even never display) bad reviews for companies that pay them.
Also, no matter how good an employer is, there will be some employees who just can't be satisfied. Only the absolute worst employers would have no good reviews, since there are people out there who are so desperate that they would rate a place with very low pay and an 80 hour workweek well if it came with 3 meals a day and a free bunk in a dormitory.
Check what their forums and reviews say about their Top Howevermany Employers. If the review for those are 10/10 (with one or two 8/10 and 9/10 reviewer ratings to add realism) and few, if any, complaints in the forums, that's a very strong indication that the site is not presenting an honest picture of selected companies.
Since you are already in China, if you see what looks like a good school, don't settle for just a phone or live chat iterview. If they are interested in you and you are interested in them, go for an onsite visit. Before signing a contract, ask to meet some current foreign employees. Invite one or two of them out for coffee, beer, or baijio just to get them away from their supervisors. Chat a bit and see what they really think.
One other note that should be considered a Commandment for FTs. Never trust a recruiter. Never trust any recruiter. This even includes members of fine establishments like the Saloon who can seem like nice and helpful guys in the forum. Recruiters lie. Recruiters cheat. Recruiters steal. If there is a problem with the employer, the recruiter is not on your side or the employer's side. The recruiter is always 100% on the recruiter's side. If there ever were any honest recruiters, they were quickly murdered by the dishonest ones. ALWAYS ALWAYS ALWAYS deal directly with the school/company that you hope to be hired by.