Mike,
Having owned, raced, and ridden both types of rims, I have not noticed a difference in the turn in with the Magteks.
I have held one of each type of rim at the same time, and the difference isn't that great. Of course even a pound is a pound of rotating mass, but I haven't noticed the bike feel any different from one to the other.
Since the Magtek isn't a Mag rim like say a Marvic, the weight savings isn't that huge. Honda had to make the rim last up to years of road use, in order to not bring a huge liability upon them.
Once you start talking about closed course race specific applications, the liability drops a great deal, and Honda can use lighter material, that has a lesser life span.
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Charles Gallant