Man there is a lot of silly macho posturing in this thread.
I know a pistol may be a phallic symbol to some of you, but come on guys, talk about over-compensation.
The question really is basic.
1st.
Does he want to be a gun owner or a competent shooter?
If he want to be a competent shooter then he needs to practice the fundamentals of basic pistol marksmanship.
He will need to practice these for thousands of iterations if he is ever going to become a "good" pistol shooter.
He also needs a good dry-fire regimen.
So caliber choice should be evaluated under this paradigm.
Optimally, the novice starts with a rimfire handgun and then quickly proceeds to a centerfire handgun.
The rimfire is retained to increase volume of practice and to decrease associated costs.
The choice of centerfire caliber is not nearly as important if the shooter is already developing solid fundamentals on the rimfire platform.
Cost may be a consideration when choosing the centerfire caliber. This is especially the case if the shooter has no intentions of reloading and has no shooting partners that reload ammo.
If the cost of ammo is prohibitive the amount of practice will decrease.
If the shooter has plenty of money or access to cheap reloads then it doesn't matter what centerfire caliber he transitions to, as long as his use of this caliber is not hindering the development of solid technique.
The fact of the matter is, if you have solid fundamentals you will know if a particular caliber is inducing a flinch.
If you don't, then you won't.