I like A Closer Look. They don't have a lot of shops in my area, but I've done a few for them. When I had questions/needed clarification, they responded super fast AND they've randomly bonused a couple shops after I've submitted - I guess because my report was very good or detailed (I keep a spreadsheet where I enter shops, reimbursement, pay, etc., so, I know those shops were NOT advertised as bonused when I signed up). It's just nice that they monetarily acknowledge my effort.
I also did a bunch for MarketViewpoint - very responsive to questions, and good feedback. Because of rotation limits, I've basically sucked their job board dry for a while, though. Servimer has also been very responsive, and gives detailed, specific feedback, which I appreciate.
And then there are particular schedulers I like at various companies for the same reason, and some I try to avoid because I feel like I'm floating in the wind if I have a question or need to cancel (for example, I legit had covid and had to cancel a shop, and even though I offered to send documentation, and did it as soon as I knew - before any due dates - when they cancelled the shops, they gave me lowered ratings for not doing the shop).