new rv purchase
Hardwood cabinets are really nice, but they add to the price and the weight of the RV. Particle Board/MDF is lighter and cheaper, so more common. The downside is 1) they give off small amounts of noxious gas over time (and more noxious gasses if they catch fire), 2) They absorb water and swell and 3) they don't have the tensile strength (breaks easier) or screw strength (screws pull out more) that hardwoods do.
For 1), even if you get hardwood cabinets, there is a fair chance that Particle Board/MDF will be used in the trailer construction, so the cabinets may or may not be a significant factor. Also, if no one who uses the trailer is sensitive to these gasses (formaldahyde, I think), it may not be as significant a factor. For 2) (and 1 as well), check that the laminate covers all surfaces AND EDGES to keep the water out (and the gasses in). For 3), it depends on how long, how much and how hard you will use the unit. The same cabinets could last 1 family 1 year, and another family 30 years.
What it comes down to is personal choice. I, for example, hate particle board with a passion beyond reason, and will not allow it in my house under any circumstances (oddly enough, I don't have much furniture

. But my RV is filled with particle board, because it was the only trailer I found light enough and cheap enough for my needs.
I was under the impression that all standard RVs had the same level of insulation; then you could step up to an 'artic' package if you wanted more. I could be wrong and they might in fact vary, even widely. But it seems that the problem is that even if your cabin is toasty warm, you need to keep in mind the effects of weather on the 'outside' of the living area - tanks and piping in particular. So before I worried about insulation, I'd worry about what weather resistance (enclosed/heated) was provided to the water/sewage systems.
I wouldn't use the wheels in making a purchase decision (unless they were a 'tie breaker'). Stainless steel may be nice, but not critical, and in any case, you can 'easily' replace wheels.