It is absolutely true that a well-made composite boat is stronger than many on this board assume. For your stated purposes either an all glass or a Kevlar/glass boat should hold up very well, assuming it was made by a quality builder.
For the matter of that, I have two all Kevlar, gel-coated boats that date back to the 1980s that have done very well. They are not light layups, not foam-cored, and they have seen a fair bit of river use. Kevlar is not going to abrade and fuzz up overnight and gel coat provides a good bit of abrasion resistance. If the gel coat is starting to wear through it is not that difficult to either repair it, or cover the abraded area with a layer or layers of fiberglass before the aramid cloth abrades.
As said, a fiberglass boat can be very strong, or it can be crap. Chopper gun fiberglass boats are typically heavy, brittle and weak. Kevlar boats can certainly be cracked as well. In my experience, boats with aramid interiors are less susceptible to catastrophic failures but the aramid fibers, though they may well remain intact, tend to separate from the resin matrix to the extent that water might leak right through the cracked area.
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