If your 38 is the 3-slide (looks like it in the thumbnail) you have 3 parallel slides (floor doesn't go flush after extension, but stays @ same level in or out). W/that I'd say flex or no flex, wouldn't enter into the flooring decision. On a flush-floor slide the slide comes carpeted regardless, cuz the seamed carpet flap is used to overlay and hide the flush-seam in floor.
We've had "Alloc" brand @ home; good stuff. Replaced w/prefinished maple when the washer leaked & swelled the joints. I'd guess any of the "Pergo" type products that are made w/particle board substrate will swell if water is allowed to lay on the seams very long. Otherwise, its like having hard formica floor in a pattern of your choosing- very durable, very cleanable.
Baja-tested '08 2-slide 36'
Alpine: The Ultimate DIY'er Project