I'm by no means an expert on this, but have lots of experience with the magnus and other cut to the point, 2 blade heads.

The magnus heads are very reliable and strong. As far as accuracy is concerned, it really depends on how well your bow/arrow combo are tuned to each other and the size of the fletch/vanes that you use. With my longbow/recurve, I don't have accuracy problems with the heads. They fly same as my field points. Mainly because I tune my bow with broadheads, not field points. The spine of the arrow and size of the fletching are also very important for good and consistent flight with broadheads. If the arrow flies stiff or weak or the nock point isn't located just right, then the broadhead is going to magnify these problems with inconsistent flight. The smaller the vanes, the more the broadhead will want to steer the arrow and the larger the vane, the less the head will be able to steer, but you will still have problems if your bow is not properly tuned to the broadheads tipped arrow.

In my opinion, on deer sized game there is no advantage to go to a 2 bladed head, especially if the bow you are shooting is prone to somehow getting out of adjustment when bumped or just because it has moving parts and something comes loose, or if you are having problems with finding a compatible arrow spine. You are much better off sticking with a head that is consistent in flight out of your particular bow.