They serve the purpose. I am not sure how they match up size wise against a versi-plug or whatever. The hole is a bit small so some debris can get hung up in it. (But hopefully you aren't getting debris in a ski like you would in an open cockpit style kayak)
I've had them for probably 15 years and they don't leak yet. The only concern is pulling the plug all the way out and maybe losing it. On the kayak there is a thin rubber 'rope' that tethers the plug to the kayak carrying handle/straps. It ties from the strap through that little slot in the plug's knob.
Of course on a kayak they are on top of the vessel, they don't stay submerged 24/7 like they would on a ski.