What would be the difference between using a slip-on ferrule with a proper tip installed onto that slip-on and playing with that slip-on, as opposed to just regularly installing the tip onto the cue stick? (Let's say theoretically I have plenty of money to spend, and I decide to install a kamui onto the slip-on ferrule and compared it to a kamui installed onto a stick regularly?)
Slip ons are junk. Would you rather have a thin piece of plastic, poorly fit with vibrations in it and sketchy contact with the stick, or a solid piece that is "one with the stick?"
Slip ons can work, but they are junk for anyone serious about the game. If you have to or are on a tight budget, use them and don't worry about it. They are better than wood and most bangers don't know the difference, after all, most bars have them. You can have fun with a slip on tip. It's not ideal, but let's be honest, only 5% of the people that play pool are serious.
If the ferrule is damaged and it's above your ability to fix, or you don't have the tools, don't want to pay a cue guy to fix, just use a slip on, especially since you don't own them. But if it were personal cues, even house cues, they are never worth using. An elkmaster costs 50 cents and super glue gel is cheap. You can retip with a simple "tool kit." look up Dr. Dave on youtube, he has a recent video showing how to do a good job with a knife, sandpaper, and glue. It's not hard and unless you are repairing SERIOUS damage, you can do it and 50 cents worth of tip is much better than 50 cents worth of slip on. Hell, treat yourself and put a triangle or le pro on for a dollar.
EDIT: Yeah, cut the rounded crap off with a knife and high grit (fine, not rough) sandpaper, like the wetsanding stuff for cars. The only thing you have to worry about is that the surface is level and not cockeyed. If you have access to slip ons, it might be a good idea to put them on temporarily so idiots don't tear them up before you get a change to re-tip them. Super glue gel is the key, I use gorilla brand but any works. Look up Dr. Dave's thread here too, lots of good info on replacing tips.