There was an article a couple few years back in Muzzle Blasts about caps.
The big thing is a combination of flame velocity (basically volume of material related) and flame temp (composition of the material related).

Ultimately cap selection boiled down to ignition design and powder type vs. these 2 factors.

Some traditional breeches like drum and snail designs have a long tortuous path to the powder requiring a tad hotter cap with a relatively intense flame. Most in lines dont have this but have issues with length and diameter to the charge which can be comparable problems.

Best bet is try each out and stick with the one that works the best in your piece. I happen to use the CCI magnums having tried the others and found them lacking. Coincidentally they happened to have the an average flame temp but the highest velocity of the types tested in the article.

Keep yer powder dry,
D.