Having used both a HD camcorder, and a GoPro for various things on vacation, I MUCH, MUCH prefer a small camcorder for a number of reasons. They each have strong advantages for certain uses, but the camcorder wins by a long shot for most things I want to take video of on vacation.
A camcorder is much easier to use. Flip it open, hit record. When done, just flip it closed and tuck it away. You can easily see exactly what you are recording. Plus, you typically have tons of optical zoom, ready when needed. The audio is typically much clearer than the GoPro. The GoPro tends to get lots of scuffing noise from being jostled around so much. Not so with a camcorder.
The smaller HD camcorders from Sony, JVC, and Canon easy fit in my side pocket of my cargo shorts. Easy to carry, and ready whenever I need it.
GoPro's are great for strapping it to your head or chest for ride video when you truly want hands free, but that's about all I would use it for. It might be o.k. for wearing on the head for fireworks also, but you won't be sure of what you are recording. Always a guessing game. Same with a chest mount. You really don't get to see what you're recording, so if you miss something, well, there's no knowing.
Dan