While I'm not trying to make it sound like swapping uppers for a conversion kit is some major undertaking (it most certainly is not
), there is little doubt in my mind that on many ranges, in many range sessions, it's clearly going to be a pain in the tuckus that will slow down your range day.
If you are a veteran shooter with a backyard range and a huge table and great weather and no set schedule, swapping uppers is a 2-minute job that is stress free, easy and even enjoyable.
If you are a newish shooter, on a publicly accessed indoor range, where you are paying by the hour for your little slot, may or may not have a sizable table or ledge to have your gun parts sitting on, may or may not have decent light above or around you, may or may not have guys on either side of you setting off large handguns and raining brass down on top of you... swapping out a conversion kit is absolutely going to be an annoyance at the least and a problematic undertaking at the worst.
A quality conversion kit can be a joy but I think if you polled 100 shooters who purchased high-quality conversion kits and have had them for a decent length of time, you'll likely find that more than 90 of those guys end up arranging a "dedicated" lower for their upper conversion. It's just plain easier to grab a second handgun to do a different kind of shooting than it is to swap out parts.
A conversion kit will certainly give top shot at the SAME feel as your center fire pistol, but the skills you develop shooting some other (entirely different) semi-auto rimfire pistol will absolutely, 100% transfer over if your goal is to make yourself a better shooter.
Unless you never
plan to buy a different center fire handgun, you'll be adapting and trying other platforms anyway. There aren't many shooters who pick one handgun and never buy another.