@BrechtSchamp is correct and I'd add that if you're just looking to do a 1:1 replacement then the MR42 is a fine choice, but it would help to know a few things to make a more solid recommendation.
Are there any existing performance or coverage or interference issues in the existing deployment, or is it to simply refresh the again equipment to the latest equivalent? Was a site survey completed prior to the existing deployment that could be referenced?
What kind of deployment is this, perhaps corporate cubicle office space and conference rooms, or perhaps classrooms in school buildings, or some other kind of space like retail or hospital or something else?
Are there any requirements around performance levels, like a certain amount of minimum throughput per client?
What is the maximum client density in any given area across the deployment, for example will it mostly be low/medium client density with a few pockets of high density like in a large conference room or auditorium? Because you might want to consider a higher-end 4x4:4 AP like MR52 in certain places.
What are the client devices (or will it be a mix like in a BYOD environment) and what are the primary applications that will be in use, such as generic web/email for guests versus internal employee applications, and do those applications have associated performance requirements? And will the wifi also be supporting voice and/or location tracking?
Sorry so many questions but if you have some of that info, we would be happy to assist further.