My model has larger differences because I used Magnesium and Titanium, which have larger differences in CTE than Steel and Titanium. Also my geometry is different with thicker walls.
Your model still had an 11% higher Normal Radial (X) stress in the Axisymmetric model than the Plane Stress model.
Plot the Normal Axial (Y) Stress in the Axisymmetric model and compare that with 0 from Plane Stress.
You can look at equivalent stress if you want. Normal stress lets you compare directions individually, while equivalent stress mixes them all up into one number.
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