I would recommend looking at
a .36 cal pocket police if you want to carry Black Powder. It is significantly lighter and more compact. Of the two you mentioned, I would go with a Short barrel Colt. I have had too much trouble with the caps wedging in the frame, preventing cylinder rotation, for me to trust the Remington style.
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I'd agree with this. My Pocket Navy is the factory conversion to ,38 rimfire, with "36 cal" still on the trigger guard taken from the cap and ball parts bin. It is delightfully slim and light, which I think is far more important in a carry gun than length, and its 5½in. barrel would give considerable velocity. It points extremely well, and although I prefer the Army grip to the Navy, the little 1862 one is as good as any which doesn't permit a full three fingers grip. A Remington would be noticeably bulkier than a Colt.
Incidentally I think the .38 rimfire conversion in this size was a bad one, good though the cap and ball version was. The steel is paper-thin over the cylinder notches, and I think burst cylinders probably happened. It was unlikely to be dangerous, and no doubt a replacement cylinder was cheaply available, in the days when they weren't valuable antiques.
There are two factors in a cap fragment jam. One is where the fragments go, and I am sure the Colt is at best equal to the Remington in this respect. The other is the fit of the caps on the nipple, and this can be taken care of with replacement nipples. You can also use a piece of soft rubber or plastic tubing over each one, which should help and also reduces any tendency to moisture absorption.
The Italians have made various fantasy revolvers which never really existed before, such as "Thunderer" style round butts for the cap and ball revolvers, and non-factory barrel lengths, often with no rammer. I think the round butt is the one that is worth having, but it is probably available only in the Nave and Army sizes.
I suppose a lot depends on what sort of carry. France has less than a third the homicide rate of the US, and I think the difference holds up pretty well with knife, hammer and rock in old sock homicide. The disparity is probably much greater in the field of deadly assault on innocent crime victims. So permanent highly concealed carry, as a lifesaver, probably ranks with the portable heart defribillator. Northern Irish undercover practice (not mine but of people I knew, and the IRA had on a list) used to have a carry pistol and a car pistol. That is probably a far more viable option than a spare cylinder, although I don't doubt that a carrying device could be made to protect the caps.
Here is a website in France which I have found extremely good, which has plenty of parts for cap and ball revolvers.
https://www.naturabuy.fr/
https://www.naturabuy.fr/