I had 11 rvs in my time with 1/2 being non slide units and 1/2 with slides.
It's pretty simple. If you NEED more room then get a slide unit. Many people just like the extra amount of room and don't care about anything else.
The general rule . LOL
If one person goes shopping for an rv, they end up with a non slide unit. If two people shop, they end up with a slideout in order to save the marriage.
Availability and rv selection:
The rv industry revolves their floorplans around slideout models because they offer more room and people like that 'being at home ' feeling. The market is flooded with slide models and they have gotten better over time. But basic design flaws are still present because it's the nature of the beast.
Keep in mind if you talk to 25 rv owners to form an opinion that opinion might be a lot different if you talk to 250 owners.
With that being said , I prefer no slides. (Remember the Lance sagging slide problems they had ? ) Especially after having two friends that owned rv dealerships. I spent countless days over the years hanging out chatting with lots of rv owners and seeing the problems MANY OWNERS have had fighting with the rv manufacturer who were trying wiggle out offering warranty help. The manufacturer matters and having a good dealer that might have to dig into his own pocket to help a customer is what makes rv life go round. Some manufacturers tried to push the blame onto the owner. (I know that didn't happen with Northstar TC's, S&S or Snow Rivers ) So that plus my personal experience is what I based my decision on.
Using the rv:
My slide experience made it colder inside the rv on those cold days/nights, making it more difficult to heat.Propane use increased. I used a lot less propane with my non slide rvs. Many times I had to close the slide at night to keep it warmer inside.
I also had to climb onto the roof in a light snow to clear off the slide roof before I could pull it back in. The very thin hardly insulated roof of a slide caused the snow to defrost then freeze. I had to chip the ice off in order to close it. That got old real fast.
Slideout toppers didn't help. Wind would blow the snow under the topper and trap it, making it even more difficult to remove.
I was able to heat my rvs using an electric heater but not with slideout models.
Slides are weight and some rvs run at max GVWR as it is. You might have to be very careful to not overload the rv when packing. It might mean NOT carrying water.
I never liked the idea of cutting a huge hole in an rv sidewall. It weakens the wall, can cause the framework to flex where the slide could bind, go out of alignment and not be able to slide back in. I have seen the exterior filon crack when the framework is stressed.
A motor is involved and inexpensive 12v motors have been know to fail. I have seen a lot of replaced motors.
Slide motors can be stressed by slides rubbing on carpets or being off alignment. That's a contributing factor, having motor overheat due to increased friction.
I have also seen wires cramped under slides causing electrical issues due to the slide movement.
A fridge in a slide has to be vented out the side which would need a 12v fan that's going to use 12v battery power. Slides with kitchens also had many issues due to movement and flex gas lines.
Many people that want a slide try to protect themselves from costly repair problems by looking into extended warranties.
If you are thinking about an extended warranty it might be more costly if you have a slide model, but that would depend on the company offering the service contract that includes very specific language that's usually not in the buyers favor.
I do not like aftermarket warranty companies. I think that's a bad idea, too many gray areas and the possibility of them going out of business.
Good luck with your decision. I hope my experiences offer some insight. These are big investments . At the end of the day, you have buy what floorplan offers you what you need.
* Make sure that floorpan can be used with the slide 'IN' ...just in case you have to operate that way until a repair is made.