While I'm not an expert on CPAgrip, I can tell you that the differences between these two are extreme. They are completely different companies.
Whilst CPAgrip is for incentive CPA, MaxBounty strictly prohibits the use of incentives.
CPAgrip has, to my knowledge, a modest inventory of offers if perhaps on the low side. These offers are also re-brokered from partners that they work with and available likely to all of the other networks.
MaxBounty has a deeper inventory and procures exclusive offers that are unique to their platform.
There is nothing that stands out about CPAgrip as either good nor bad if you are interested in incentive. There are also multiple other networks for incentive that may serve you well.
With MaxBounty, there are other CPA networks but the speciality is their unique and exclusive offer selection.
It truly comes down to the type of traffic that you are working with given that these businesses are so dramatically different.