For those canoes offered in both versions, like the Mad River Explorer, advantages of one over the other?
Royalex is lighter, often stiffer.
Royalex is much easier to repair.
The weight difference is usually enough, alone, to make the decison.
“Plastic” is somewhat more resistant to damage, but it can be damaged, and because it is crosslink, it doesn’t weld well and is very hard to patch.
“Plastic” is cheaper, but you can see why you might pay more for Royalex.
By “plastic” you mean single-layer poly?
Also, the single-layer plastic hulls tend to warp in the sun much more easily - thereby taking on a shape that is less efficient than what was intended. Also, some of those hulls are built with plastic so thin and flexible that interior metal framework is required for it to hold any usable shape at all (Coleman, Pelican). That isn’t as big an issue as the fact that this kind of hull isn’t really designed for paddling as much as for stacking for cheap shipping.
Warping and Weight
As mentioned, poly boats weigh quite a bit more than Royalex, which is really something to think about when you consider how darned heavy a Royalex boat is. There's at least one person on this board who says poly boats don't usually warp, but except for brand-new boats, I have only seen ONE poly boat that wasn't warped (really badly warped in most cases), and I suspect that the single non-warped boat I saw was stored under ideal conditions. On the other hand, I have only seen one Royalex boat that WAS warped, and the nature of the warping made it clear that it was caused by being tied tightly on a roof rack, probably much too tightly and for much too long. Unlike nearly all the poly boats I've seen, a Royalex boat won't warp simply because it is several years old or because you left it in the sun too long.
Get the Royalex.
You’ll be happy that you did in the long run.
Bob + 1
Yeah, I have a OT Pack in Royalex and I take it down very rocky rivers and i fish so I run into rocks and ground out on ledges to anchor while I fish. The Royalex flexes and takes the scrapes really well over plastic boats I have had in the past.
I did add kevlar skid plates on each end.