Despite similar fan layouts, these two games do not in my opinion play in a similar way. Yes, you do destroy a central object five times, but that's the biggest similarity. I have an AFM and find it's game play fast and furious. I have played MM a lot, but crossed it off my list because the game play is not to my style of liking. MM is a fun game, and the humour is a little better than the AFM humour, but I don't like the ramp shots as much, and the trolls are problematic sometimes, with balls getting caught as they go down. Merlin's Magic is like AFM's Stroke of Luck, but it's one of those traps with a wire gate, not as satisfying as the clunk you get into AFM's Stroke of Luck upkicker, which is also a more fun way to return the ball. I find the shot to the MM catapult to be too flukey to achieve.
I bet there's as many people though that prefer MM over AFM for similar reasons.
It's really a matter of taste - there's enough different about these games (particularly the theme and humour) to make owning both worthwhile, so get some game time on AFM if possible to see if it appeals.
