I think people have different answers for this based on different factors. I might like an MSC that pays more than another, so my answer is that MSC based on pay, but I might like another MSC better because I have a better relationship with a scheduler(s) so I get better opportunities.
I like IPSOS very much for several reasons. Sassie SELF-ASSIGN and pay is decent if you are patient. Karen is one of the more professional schedulers out there. IPSOS pays quicker than most MSC too. There are reasons to not like IPSOS (like NO responses to general mailbox), but I've learned they suck with that, so I don't bother and I just take the ones that I don't need to ask questions or get help.
I like DJC because they have a good west coast chain and their schedulers are awesome. The pay is below average, but I don't mind doing their shops. They also pay very quickly. They are a very "hands on" group that is very helpful.
I pretty much like any MSC that has self-assign and no stupid tests or certifications to prove I can still shop after 20 years.
I do NOT like MSC with lengthy reports and too much narrative. There is a $40 shop fee restaurant on the board now for Coyle. I'm debating doing it. $40 plus reimbursement is nice, but I don't know if I want the headache for the $40.
I won't work for Bestmark or any other company that cannot seem to pay their shoppers. Plus Bestmark software blows.