I've been shooting muskets in competition for 10 years.
The best caps are RWS Dynamite Nobel. They have been hard to get for about a year.
The Schuetzen caps are OK. They are, however, made of steel, and then brass plated. You can prove this with a magnet. Being steel, they do not always hammer down onto the nipple as easily as they should, and I could not get reliable ignition with my Pedersoli Sharps until I replaced the nipple. I tried filing down my old nipple to no avail.
Also, I think because the Sheutzen caps do not hammer down tightly onto the nipple, they there is a lot of cap blast blow-by that will pepper the fire out of your fingers on your off hand. It's enough stinging and long-lasting that you will either wear a glove or start altering your hand position when shooting.
CCI got sued about 10 years ago when a cap fragment hurt someone's eye. They then weakened their caps. For a while, they were labeled "FOR REENACTOR USE". Later, they were labeled "GENERAL PURPOSE" but if you peeled off the top label you'd find the old "FOR REENACTOR USE" label underneath. The CCI caps are now weak. They do not reliably fire any gun that has a multi-angle fire channel (Sharps, 1861 Springfield). They will generally work OK in any gun with a straight-in fire channel (Enfield, 1842 Springfield).