I did a somewhat larger test. By the looks of it .is_a?, .kind_of? and .class are pretty much the same. I take the differences due to other system factors at the time of execution.
AT - SpeedTest:
is_a? - 0.89c
kind_of? - 0.782c
class - 0.875c
typename - 2.297c
Model Statistics:
edges = 159630
faces = 61300
groups = 0
components = 1000
construction_lines = 0
construction_points = 0
images = 0
section_planes = 0
texts = 0
others = 0


