What different experience do you mean?
PUG'ing your KSM is in no way different to fixed groups. People expect only to time it, with basic pulls, loose group composition and all you have to do is play without to much failing on simple mechanics.
A fixed group is easier, if you get carried, else its just like PUGing. You don't do MDI like pulls with 210 ilvl and without endless practice and its clearly not needed for KSM.
And PUGs are fine with the normal ilvl/rating requirements for 10-15 keys (200-215 ilvl, rating from 800-1200) everything less is asking for a free carry.
And this is my POV on the alliance side, you can queue at any time, for specific dungeons, at specific key levels and you get runs going deep into the night. Horde got 20x as much activity so I dont get the PUG vs fixed group nonsense for KSM.
You need 5-10 keys at least for the weekly vault min-maxing for easy gearing, why not just spend every week for +1 key levels and progress like everyone else?