I use a marine grade epoxy called Marine Tex. It's available at most boating stores. Initially it is about the consistency of silly putty, but when you mix in the catalyst, it becomes the consistency of toothpaste, so you just spread it on and wait for it to set. Then you can sand it smooth. It's about $15 bucks for the kit. DO NOT get the fast-set formula, as it sets up too quickly and you'll be rushed.
It comes in white and grey. If you wanna be totally obsessive, you can get white and tint it with color, but I wouldn't recommend it because lots of work and the color tint is expensive.
I've done lots of wakeboards with this, and also numerous patches to Surftech Tuflite boards. Have not had a patch fail on me yet. I've got a half dozen patches on my white Surftech, and you can't even find them. I did my buddy's Surftech in a tinted light blue, took some time to get the color right, and then I polished it, you can't see it unless you're looking for it. For wakeboards, I'm not that obsessive. I usually just roughen up the area to be repaired, mix it up and slop some on like bondo, neat trick is to then gently and lightly stretch over a piece of saran wrap so you can smooth it and work the contours, leaving the patched area just a little bit high. Tape the saran wrap in place when you are happy with the contours, then after the epoxy sets (over night), the saran wrap peels right off. You could ride it just fine like that, but I usually sand it down just a tiny bit more to really get the edges perfect.
IMO, Marine Tex is tougher than the sun-setting epoxies, and Marine Tex does not yellow over time like the clear patching products do.
Only bummer is you have to mix the whole kit and use it all at once, so you are unable to save part for future repairs, thus there is a bit of waste involved.
Good luck, which ever way you decide to go. Try the saran wrap trick. Surfer who sold me my Surftech showed me that, and it works like a charm.