30 vs 35 spline axles

35 spline is not bigger according to Cass. aka Doctor Diff. as the take the same green bearing. 40 spline is way bigger, u need to use Ford axle ends and brakes to use them. 23 spline is a 1 in shaft. 18 spline is a 1 1/4 shaft. Kim
I thought the splined end would be bigger? is this so??