I can't presume to suggest a definitive answer for anyone else.
I own 7 J-frames, and after borrowing another instructor's LCP, I bought one of my own.
I see the J-frame as being a more versatile retirement CCW handgun ... for
my perceived needs.
My assorted J-frames (of which 2 of them are 642-1's) can use heavier bullet weights than the LCP can use. I tend to think the heavier bullets, combined with some of the more modern designed hollowpoints, give the .38 Special (especially in +P) a potential "performance" advantage (and I'm not talking about muzzle energy).
Also, as a longtime revolver shooter I can shoot them somewhat accurately & effectively. I find them easily used for rapid shot strings at ranges from 2-12 yards, slower aimed head shots out to 25 yards, and I can consistently hit steel silhouette targets out to 50 yards with different loads in the DAO J's.
Not everyone enjoys a similar experience shooting the snub 5-shot .38's, though, so it's pretty dependent on the user/shooter.
Now, the diminutive size of the LCP allows for some concealed pocket carry in some of my jeans which won't let me conceal one of my J-frames. Beats not carrying (or carrying a .22 or .25). That's the only reason I bought another .380 after a 25 year hiatus from the caliber. (That and much smaller models now being available compared to the Beretta M84 I tried many years ago.
)
I see the LCP as a reasonable alternative, in an anticipated "low threat" environment, to carrying the possibly "more effective" retirement weapon, meaning one of my J's.
Yeah, I know any number of folks will now demand to know where I got my crystal ball, or how I KNOW that TODAY isn't the day I'll need a "full-size fighting handgun".
I don't have the gift of clairvoyance. It's just that having carried a badge for 3 decades, more than 20 of which have also been as a firearms instructor, I've developed some small amount of training and experience upon which I feel comfortable basing
my choices, for
my needs and daily activities.
I plan to carry the LCP in those instances where my clothing & planned activities won't allow me to carry one of my J's (or one of my assorted 9's, .40's or .45's). I no longer have to dress around a duty or plainclothes weapon. I can choose as I will, for the reasons I decide are appropriate for me.
If for some reason I were required to choose between my J's and my newly acquired LCP, I'd keep the J's. No question.
That's me, though.
Suit yourself.