What we are talking is a diff. of .062 secs..
This may make the slightest bit of difference from a "Benched rifle", I would say the diff. would be negligable from a standing position "Off hand".
Try sticking a laser pointer in the end of your barrel "Empty of course" even at 30 yds. with a one inch dot off hand the dottle factor is amazing.
In my case I try to catch the sights as they are passing through the dottle area and squeeeeeze. To each his own but I really do not think .062secs. is going to make or break when there are so many other Larger factors at play.
As to the waterproof and reliablity I have nothing to offer in experience.
I say shoot what you like and like what you shoot. 
I suggest you shoot some 50 ft smallbore with a 6-8 power scope on 2 different rifles. A fast lock time 22 and a slow lock time 22. Even a Small-Martini action verses a Stevens 44 for example. There is less time difference here than the flint verses perc but there is a significant difference in the scores on the target. Yes folks I have shot both. I shot the Martini all winter one year every weak 100 rounds or so in competition.
The Martini was fast enough that the bullet hole was always where the cross hairs were when the trigger broke. Even with the slightly slower 44, fast compared to a 1874 Sharps, there will be shots that are not "callable" you know where the cross hairs were when the trigger broke but the bullet hole is someplace else.
I have had one percussion gun that consistently had a "pop-bang" firing cycle. This puts it into the flintlock firing cycle. I have had others that were very fast like a modern fast lock time CF gun.
FLINTLOCKS ARE NEVER THIS FAST.
The breechloader/percussion ignition cycle is striker/hammer falls from cocked to the primer, primer fires and shoots a high pressure jet of fire into the propellant.
The only thing that can slow this is a gummed up firing mechanism or a convoluted/improperly designed flash channel. This is what will produce a "slow" percussion.
Flintlock cycle.
Cock moves off full cock and drives the flint into the frizzen, the flint tears metal from the frizzen and in the process the metal is heated to a temperature above the ignition of BP. The ensuing "sparks" are thrown or fall into the pan, they heat one or more grains of powder to the ignition point, the flame propagates. The heat builds and the HEAT then ignites the powder in the barrel/vent.
How ANYONE who has shot both can consider the FL to be faster is just beyond me. I have shot flint and percussion guns since 1965 or so. NEVER have I EVER thought flint was faster than percussion. I have some "fast" flintlocks. If I shoot my AR for a few days a "fast" flintlock is painfully slow. If I shoot nothing but flint they are really fast.
The tests show that the percussion is 6-7 times faster. 6-7 times. This means the centerline of the barrel can move 6-7 times as far before the projectile clears the muzzle. Its why flintlocks are harder to shoot well.
Dan
