Flintlocks in excellent condition are not faster than caplocks in excellent condition. They are slower.
By the time the flint has started to bite into the frizzen to make its first spark, the fulminate in the caplocks cap is firing.
By the time the powder in the pan is starting to ignite the caplocks cap flash is reaching and igniting the main powder charge.
By the time the flintlocks flash reaches the main powder charge and starts to ignite it, the percussion guns ball has left the barrel.
Now, when all is said and done, if both styles of guns are working as they should the actual time difference between the two will be so small that the human mind cannot recognize the difference.
Enough said.
As for "which one is easier?" the caplock is.
Loading the main powder charge and ramming the ball is almost identical, the one difference being that the caplocks hammer should be at half cock.
Placing a cap on the nipple is much simpler than pouring the right amount of powder into the flintlocks pan and making sure it doesn't block the vent hole.
Also, there is no need to close the frizzen, or to "pick the vent" which is a recommended procedure to get a flintlock to fire as quickly as it can. There is no need to adjust the flint or to re-knap the flint.
The shooter only has to have a supply of percussion caps of the right size.
That said, a flintlock which has a vent located directly in the side of the barrel doesn't have much of anything between the main powder charge and the flash of the pan so there is not much to prevent the main powder charge from firing.
If the percussion gun has a simple side drum on the barrel there is just a short hole between the nipple and the main charge.
This short hole can become saturated with oil which will "kill" the gunpowder that gets into it and make the gun "hang fire" with a noticable delay.
The current crop of percussion guns that use a powder chamber (some call them a Patent breech) has a much longer path for the flame of the cap to travel and if this longer path is oil soaked or plugged with fouling it can prevent ignition or cause hang fires.
There are a few flintlocks on the market that also have this same type of powder chamber breech and they are even more prone to problems than the percussion guns are.
The Military style of percussion which has the nipple screwed directly into the top of the barrel and the underhammer which also screws its nipple directly into the barrel are the fastest of all.
Assuming the percussion guns bore and powder chamber (if present) is clean and free of oil or fouling they are the most reliable type of muzzleloader made.