Looking through pictures and found this one which i thought was interesting.
This is comparing the Onefinity, X-Carve, and Shapeoko 3 cross-sections.
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I’ll take the case-hardened steel 8 days a week, please… 
I think a more interesting feature would be to calculate total surface area that the bearings actually make contact with.
The 5mm thick Shapeoko extrusion is an extremely supportive cross section. I chose the smallest machine in the Shapeoko range because it would (empirically speaking) mean less tendency for the rails to flex. Now I use the SMW fixture plates and stiffener bars, I found the set up is about as rigid as one could expect from a hobby machine. I have been able to machine 6061 down to about 10𝛍m (0.0004")
Awaiting my new PwnCNC spindle, I have already purchased some ER20 collets from the original manufacturer (REGO-FIX) and they all have an indicated TIR of <5𝛍m (<0.0002"). I am looking forward to machining many metals to a high level of accuracy. REGO-FIX also supplied me with notched ER @20 collet nuts balanced for high speed spindles. I bought a 40 ~200 Nm Torcofix II torque wrench for eliminating doubt when collet nut tightening. They even had collet nuts that are balanced for spindle speeds of 100,000 RPM!
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