So what's the verdict? Do they penetrate as well as fixed blade heads or not?
Not many 1.5 - 2" diameter fixed heads on the market. So hard to measure apples to apples.
Why? It seems like penetration would be easy to compare.
Penetration between a 1.5" cutting diameter 3 blade head and a 1.125" diameter 3 blade head isn't really a comparison. The smaller diameter is always going to penetrate better. In this case near 25% better assuming blade angles are equal. Over the top swivel expandables might lose another 2-3%. Some bad ones maybe another 5%.
But penetration among adult male bowhunters is rarely the issue with expandables. Reliability of function and remaining unbarbed are the more important issues. Rage probably fares as well as any expandables in that comparison. But, one would have to legalize some and not others if such performance was a defining solution as to whether they are legal or not. That would be a nightmare!

Always better to have a fragile expandable that penetrates 25% less but is sharp than a fixed blade that is dull. And since we can not control the use of properly sharpened heads then all non-barbed heads should be legal regardless of fixed or method of blade deployment. Trying to regulate stupidity out of society has never worked before. So why then should it work on the select few bowhunters? Increase minimum draw weight on elk to 50# then legalize expendables and be done with it, IMO.
And while we are at it let's throw out the ridiculous 6 grains per pound arrow rule too!