I’m glad you enjoyed it! Lemme see if I can answer your questions:
I’m going to split your question into two parts. First is the shape and the second is the material.
(Remember that MOE is a property of the material, and inertia is a property of the shape, i.e. dimensions.)
Bending moment of inertia for EMT
You’re on the right track but I wonder if your calculations are fully correct. Did you maybe use diameter^4 instead of radius^4 when calculating inertia? Here’s what I have:
I_emt = pi/4*((.922/2)^4 - (.922/2 - .065)^4) = 0.0162
I__ss = pi/4*((1.00/2)^4 - (1.00/2 - .065)^4) = 0.0201
0.0201/0.0162 = 1.3 → 30% increase when going from EMT to 1".
That’s such a huge change in inertia for what just an 8% change in diameter. That means that for an identical material (and thus identical MOE) you wind up with a much less stiff tube with the EMT dimensions.
Modulus of Elasticity for EMT
So we know that the inertia for the 1" tube is 30% higher, what about the relative stiffness (MOE) of the materials? This is somewhat harder to calculate, because we don’t know the alloy and need to guess a bit. I’m guessing from your comment about drilling that this is probably mild steel with galvanization. Googling on bing.com suggests that it’s around 200MPa, which is right in line with SS. So from this perspective, EMT and SS tube don’t significantly differ.
It really comes down to that tube diameter.
Is this consistent with real-world tests?
A 30% change in inertia with 0% change in MOE means that you would expect 30% more deflection for the same load. And that’s exactly how we go from having a tiny deflection we can hardly see to something that’s really noticeable. If you haven’t seen them already, check out the visible difference in the tests for EMT and SS, both with 0.050" wall thickness: Stainless Steel - Quick and dirty flex test