I agree,
If alloy pipes are prepped right and welded by someone good with a tig, there should be no inner dags at all with very smooth change from one pipe to another.
I'll always use mandrel bent alloy, when i/c pipes are concerned. Some say it look s/house, but it can be polished very nicely... to some, polished alloy has a better "colour" than stainless steel.
Of course i think pipe route (length, number of bends) plays a bigger factor in power saving, as well as the actuall intercooler core and end tanks themselves. No use having the perfect pipes with million dollar welds and glamorous polishing if your intercooler is what is going to cost you the power!