There are a number of threads here (in both the class C and A forums) on the pros and cons of both styles. Unsurprisingly, class C's are generally preferred in the Class C forum, and class As in the class A forum.
On the whole, I think it's far more important to see what fits your needs and wants and usage rather than getting hung up on the fairly minor distinctions between the classes. Typically, but certainly not always, class C's tend to be set up more for family use and class A's for a couple. Find something with the floor plan and features that are important to you and enjoy it, whatever it may be. (Also be aware that, particularly in the Class A's, there are significant differences between the higher end diesel pusher units and the lower-end front engine gas models—perhaps greater, in many practical respects, than the difference between a front engine class A and a class C.)
In terms of service, the class C typically is a little bit easier to get chassis service done on since it's basically a standard van front end and the Ford vans are everywhere. Neither one is super convenient for chassis service; engine access is not a prime consideration in either case. Frankly, the chassis and drivetrain are likely to be among the most reliable parts of the motorhome (assuming proper routine maintenance is done).
The class A chassis is often somewhat higher capacity than the class C's, which often translates into somewhat more cargo carrying capacity or tow capability. You do, of course, have to verify such things for the particular units you're looking at.
I quite appreciate having a driver's door on my class C. Many class A's don't have one, so you have to walk halfway down the coach to exit at gas stations etc. If you're spending a lot of time traveling rather than staying in one spot for a few days at a time, that may be a consideration.