hi,
I build mine from different bom, and for some part like the Y axis, i did use Igus bearing, so, I have to design some parts that I print. Fortunately, I have a printer to do that.
The BOM help you start, then you take your own way if you can.
Anyway, both bom you mention will make a working machine.
The common things for all mendelmax are the extrusion with t-nuts and 10 mm M5. After you choose what you want, Thinginverse is full of things for this machine.
Hope it help.