I think a lot depends on how you're built and what you're carrying. Most of us have gained a bit of weight since we last bought clothes and I'll bet that if we're honest with outselves, our pants are a bit tight. Add a gun to the mix and we may have some discomfort. Looser clothing increases comfort and reduces printing.
While on the subject of undergarment holsters, I happen to like the 511 Tactical Series T-shirt with built-in holster pockets. They work great with Kahrs and similar striker-fired handguns.
While I'm done fathering little rug-rats, you younger guys just starting out must make sure you don't accidentally take yourselves out of the gene pool.
Int'l Assoc. of Law Enforcement Firearms Instructors