Model 23 three guns in one with barrel swap 357SIG, 9mm, and 40. Versatile. I’m Gen 3 fan myself and the 9mm (Glock 17/19, S&W Shield 9mm) and .45 (1911, Glock 21). How much Gen 4 23 cost?
Glock is proven platform but other striker fired pistols are good choices too. Pick platform that suits you and train. My .02. Good gun the 23 FBI has used them for awhile but they may be switching to 9mm.