Don't mean to sound all knowing, but I have spent two years reading threads and arguing with owners, sometime to the point of being thrown out of forums. During that time I got my registered tech, then certified tech, and rv inspector designations and became quite familiar with all this stuff. I did that because I felt that the critical issues were deeper than what I read in simple rv review articles and chats with salesmen and chats with 80% of the owners.
One of my red flags, these days, is if a unit uses L or S slide mechanisms. Sounds like this system, that ought to work and work better if upgraded, remains a weakness.
I think the reason the logic, I would pay more if they just put in a better slide system, doesn't work because I believe they target their market pretty closely and the quality of all of the systems and options are generally a fit to that target market. Once you start changing systems, other things get changed as well but that target total range price is what the market will most likely buy or the buyer goes down or up the alternatives.
Some RVs are designed to be used a couple of weeks a year and at the other side of that range are the full timers. Many of the rentals I worked on/repaired tended to fall apart during each rental, and worse as time went on, because they were entry level vacation units the rental company used.
Most of the buyers probably had no clue there was an issue with L and S slide mechanisms, and that is taken into consideration by the mfg as well and expected usage means it is no big deal if the prospective owner will only use the slide a couple of weeks or one month a year. Plenty of time to fix in between usages.
That is like buying a power drill at my local HD. If you pay for the cheaper drill that looks good, it works great for an occasional hobbyist, but falls apart fairly quickly when used regularly, especially on a worksite.
I mean, I think that is the way things are.
If one puts slide mechanisms at the top of their list, that would likely change the mfg products you would be looking at, but the common song sung to new buyers of new RVs, is floor plan, floor plan, floor plan.
I should add, that when you put something like a slide mechanism at the top of your list, it probably means the likelihood of buying new changes what you want such that it makes you take a significant up jump in price...unless...you get your mind around buying a used premium unit. That is where I'm at...and a bit disappointed in slowly being torn away from buying something like a new Seneca.......and no, slides are not the only thing on my list that messes with my buying decision...hydronic heat, air leveling...
Buying used, floorplan seems irrelevant to some extent as there are plenty of ways to change the floorplan within limits (and one is more apt to make changes to a used unit)