What ever you decide, visit the establishments before finally selecting.
If you were lucky enough to know for certain that you are going Airbus then do the MCC/APS on Airbus
If there is any uncertainty do it on the B737 as it is more demanding, such as no auto trim facility.
The greater exposure to multi crew by doing an APS course the easier you should find the sim ride/interview.
If you have your sights set on Ryanair then clearly go to an affiliated partner.