Ackshully... the over-fermenting that produces maduro leaves slightly reduces the nicotine content (or so I've read on the internet which never lies).

But as a poster upstairs pointed out, the commercial blenders do tend to put stronger leaves into maduro wrappers.

OTOH (there's always another hand), leaves that are darker from being closest to the sun, i.e., the top leaves, ligero, are stronger both in flavor and vitamin N. Yes, the dreaded triple maduro could make Chuck Norris cry.