David Weaver
Right, those are the difference in specs.

However, the steeper bed and much deeper body on a coffin smoother makes it much harder to do, at least when comparing to a dai that doesn't have a ledge.

At the same time, the wedge provides a little bit of forgiveness in fitting the iron to the abutments. The abutments have to be right on the dai for the iron to be snug, but that is a matter of spending the time to get it right.

I've started and stopped two coffin smoothers, and my first dai was OK. Other people may feel differently, but I think it will be harder for most to make a tasteful functional coffin smoother because of the steepness and the depth of the mortise.