There is no one size fits all.
In "my opinion" it has to do with how you use your truck camper.
We have a "run n' gun" approach. Never stay in the same place for more than 1 or 2 nights. We are constantly in and out of the camper as we travel. Lots of nights spent for lack of a better term "stealth camping".
If we were to stay in one place for more than a few nights, I would certainly enjoy the extra room and would probably buy one.
Truth be known if we ever stayed in one place for a period of time we'd probably buy a TT or 5th wheel. But for now we enjoy the benefits of a 4WD truck and the relatively remote places it can take us.
The way we use a truck camper we've never said we wish we had a slide. This is our 5th truck camper.
For those that say don't buy a slide because it will break...heck everything on an RV and vehicle for that matter is subject to breaking. Best advice if someone is concerned about something breaking while RV'ing is to stay "very close" to home.
Buy the rig that fits your style of RV'ing