I have looked into 46-0-0 for a winter app but it is somewhat a waste of money. If you are wanting to put out 1lb of N per K it is nearly impossible with this product as a granule especially in a ride-on. That would make your rate at 2lbs per k and most spreaders cannot go that low. With that said even though a 30-0-6 is a little more expensive per bag you will be able to put down correct rates for about the same amount of money per k. Another thing to think about is customer perception. If you are trying to put it down at 2lbs/k and they are used to seeing 3-5lbs/k they are going to question you and think you are skimping them. Just my opinion.
I agree that all mineral is the way to go for last apps so that the plant can absorb as much as possible before dormancy.