In that case, it really is impossible to compare and in fact I can't see how they could help. For example, there are many jobs you can get in Japan with nothing or an online cert, e.g. most ALT jobs and English conversation school jobs. All those jobs are widely advertised and any online cert provider who claims to have access to other jobs which aren't is probably lying. Other jobs will demand a proper cert or even an MA, and any online provider which claims you can get those jobs with their online cert are almost certainly lying.
If you could paste in some claims of the online providers you are thinking about regarding job placement, perhaps we could try and judge how accurate they might be.