For me, one merit is that I can rent a platform to “test.”
I decided sometime ago that I would most likely settle on one primary pistol.
Or at least just a few.
Ideally it will be pistol(s) with suitable Airsoft replicas.
If I do manage to pull this off, I will be able to train on my primary platform at home!
I can do this somewhat already. But not with the level of “sameness” as I prefer.
In considering all known variables, I most likely will settle on one or two 2 platforms.
The same type of process is going on with rifles.
There are definite advantages to limiting platforms. The main one is the level of competency it facilitates with that platform.
There are advantages to have competency on multiple platforms
But being lights out with a primary is huge!
Two pistols I am considering are Beretta M922 and Smith and Wesson M&P 22.
I know that most all instructors will advise against 22LR.
And I do not completely disagree. But I am not as worried about it as they are.
The 22LR is not perfect. But no round is.
It also has advantages that others cannot match.
I am not totally sold on 22LR even myself yet though.
Pretty much all handguns pail compared to long guns.
I suggest you read Ayoob and Wllifritz discussions on this topic, handgun round effectiveness.
For me the biggest problem with 22 is its lesser typical reliability.
It is a big factor. But all rounds can fail.
I offer you know advice on caliber. That is for you to decide!