Flintlocks are more fun and more fulfilling to shoot.
I fill the pan - more powder, hotter flash and potentially faster or more sure ignition.
In Pletch's photo tests, iirc, the pan was completely consumed & burning hot before ignition of the main charge took place. More prime, hotter flash, more consistent ignition. He also found that banking the powder away from the pan, as written in print by one author, actually slowed ignition, opposite as was claimed.
Banking the powder against the vent also increased ignition speed, not slowing it as others have claimed.
The web of steel between the pan and the barrel's main charge can have an effect as well. With my Chambers hollowed white lightning liners, the bore's charge is visible at the vent - VERY rarely have I had a flash in the pan with the main charge not going off. The odd time that has happened, was due to a piece of fouling blocking the vent, usually coming of the side of the frizzen as it was closed. If the pan goes off, so does the main charge - 99% of the time?
This might be due primarily to the proximity of the powder to the prime or coupled in concert with using a full pan for hotter flash.
Pistols usually have smaller locks, thus smaller pans, less prime. I still fill the pan of my flint pistol. It has 2 barrels, an 18" twist GM .45 that I shoot 25gr. 3F with caplock ignition and a .54 cal with 66" twist with the flint ignition in which I use 55gr. 3F to get good accuracy.
Less powder than that in either barrel does not hold accuracy to 50yards like 55gr. does in this barrel and 25gr. in the .45.
The cap-lock (change locks when I change barrels) .45 barrel also shoots exceptionally well with 200gr. R.E.A.L. bullets, making a 1 1/2" group for 6 shots at 30 yards off the bags - using the same 25gr. 3F for the charge.
I also prime with 4F.