Wood for sure, or I should say sheet material extrusions are expensive, sexy but expensive. The odd thing about core xy is it cuts resolution in half, both steppers have to move to move x or Y so in the firmware the steps get cut in half. Not sure if this has an effect but When I print with one I will find out.
I ran it yesterday at 150mm/s to watch the belts and things, it looks comical that fast. I am finding no one prints faster than about 50mm/s, 60 for the quick and dirty prints. So speed isn’t really a big deal. It just comes down to making a printer with a Z axis mounted bed. The top gantry isn’t all that important, the CoreXY is just pretty fun to build and watch and only has disadvantages when you get really big from belt tension.
I saw that smartrap core last night. When I tried that with mine the belt could actually catch on itself in the extreme position shown in the main pic on that link. That design is killer though, simplistic and gets two thumbs up from me. I want to do the Z axis differently though. This one has the longest stretch of belt at an angle directly off the empty side of the pulley which is okay but on mine caught with the gantry and could only be solved by moving the corner further away.
The smartcore from the github link has bad belt geometry. That is how I originally made mine and I know it isn’t right. There is an angle at the far side of the gantry to the corner blocks. It is not a lot but is not correct.