I dislike little percussion caps. They are fiddley to handle and first shot ignition is not very reliable. That is my experience, I know some will balk at that statement.
I find my flintlocks to be more reliable than most cap guns. Especially if a "patent" breech is involved.
For an underhammer of a side hammer where the nipple rest against the main charge relibility is much better. I have a side hammer rifle with the nipple screwed into the side of the barrel. I generally use musket caps with it. I have never had a single misfire from that rifle.
I strongly prefer musket caps when reliability matters. They are much easier to manipulate too. I would not do any serious hunting with #11s. Get the real deal RWS musket caps. CCI made/makes a sad excuse for a musket cap labeled. "re-enactor". They are junk.