This is going far afield, but I'll just state that my main reason for liking KEH over B&H, Adorama, NatCam, and UsedPhotoPro is selection. When I'm looking for something used, there is a far greater chance that they have what I want. I'd give UPP second place, but not too close. I've never found anything used that I want at NatCam or B&H so I've never bought used from them. For a while Adorama was listing Bronica ETRSi 120 film backs for $30, but they'd only list one at a time. So, one after the other, I bought three from them. Other than that I haven't seen them list anything I'm interested in.
I wish KEH had photos, but with a few exceptions, I've always been happy with what they sent, and in those cases, they took care of me. I also like playing KEH roulette--buy a bunch of AS-IS stuff for obscenely cheap to see if you luck out (I did that with a bunch of 35mm bodies I wanted to try out, but didn't want to spend much on. I also did that on some LF lenses. all of the equipment functioned with a few meaningless issues.)