I think for penetration,most should be more concerned on getting to full draw than whether using 2 or 3 blades. Even today, at 3D shoots and such, I can't believe how many guys are snap shooting before they are getting to thier anchors.
But to the question, I have always used a 2 blade head. STOS, zwickey, magnus, ribtek,grizzly....never had a problem yet with penetration. Deer, elk, stag,hogs, bison, lottsa black bears,..no issues. I wish I had a crack at a moose tag, but after 26 years of trying I think its not in the cards!
Nothing against 3 blade, I just never had a reason to switch. As I'm sure there are plenty who are the opposite of me.
Bill Carlson is a great example above. Been shooting 3 blades forever with great results.