In my opinion, 17 is Service size, meaning it'll fit a gloved hand. Glock 19 is civilian hand sized, meaning it's just big enough for a ungloved hand (At least my hands). Glock 26 size is backup size, or bloody hand sized when you have no other options. Or shower size for when you need to hide it behind shampoo bottles.
I don't want the mag sleeves because it gives me better grip, but because I want it simply as an option for when I want to use it as a mullet gun. I prefer flush mags to whatever gun I'm using. But for a subcombat, one of the options I see for it is using mag sleeves just to use as a mullet gun if I so desired, for whatever reason. I have a Springfield XDS .45 set up this way. Keep a flush mag in the gun, with two extended mags with mag sleeves if I wanted/needed it around the house instead. Kinda gives me two guns in one, if you will.