Long time Magnepan fan here and current owner of the 3.5s. But I heard the N802s at a dealer a year ago and this was one of the most impressive (read synergy) systems I have heard in a long time. The dealer really had put much effort to get this system to sing. So I know the N802s have excellent potential.
The Maggies do the mids so beautifully and the ribbon tweeter brings on qualities like few other speaker systems can touch. But the Maggies have their own problems here as well which have been covered over and over in other threads here.
There's so much said about how well the Maggies work with Bryston amps but once you hear these speakers with tube amps (200w just barely works here) you may never want another speaker again.
It all comes down to personal preference. Just keep in mind that the amp you choose is just as important as the speaker you choose here. Go into this search with an open mind and try to hear both of these in systems as close as possible to yours.
John