I think the only real advantage to keh.com vs eBay is that they have an excellent track for honoring their return policy. Now that keh.com ships internationally, there is little to no price advantage vs. eBay if you are willing to be a patient buyer.
Yes, they are conservative about rating cameras - but those ratings are cosmetic and, primarily, only have to do with wear on the finish, superficial scratches, etc.
Do not expect keh.com to reliably check the mechanical condition of any camera they are selling for under several hundred dollars - it simply isn't worth the time or cost. The last two manual-focus 35mm cameras I bought from keh.com had mechanical problems that rendered the cameras useless and neither would have required any more than loading the camera with a junk roll of film and simply testing the film transport.
I have had problems with cameras bought on eBay but I have always managed to return them for refund.
Nowadays I do not give keh.com any special consideration in my purchases.