Who pays the best?
An interesting question. If you mean strictly who pays more, it's a little like comparing apples to oranges. There are shops that pay $50-100+ but have costs. Some are video shops that require acquiring and operating video equipment, along with some added risk of not recording anything. Some involve running a credit check. Some involve lots of time, both on-site conducting the shops and writing the reports. Some have more demanding narratives. Some require a large outlay of your money which may or may not be fully reimbursed (they usually are).
If you compare the usual fees for the companies you listed I think Cirrus probably comes out on top mostly because of a certain client's shop. However, according to what is posted on the forum, that one takes hours to perform and numerous shoppers are of the opinion it is not worth it for the time spent.
I suggest the answer to your question is within you. As you continue to shop, your preferences and experience will tell you which are your favorite companies. There will be shops that you prefer to do and those that rub you the wrong way. Certain companies will be great for you while others may operate in a way that is a PITA for you to deal with. New shops come while old ones disappear or move to another mystery shopping company.
As you shop, keep expanding your list of companies to expand your opportunities - and get better shops.
Good luck.
Happily shopping Rhode Island and nearby Massachusetts and Connecticut