Neck injuries are pretty common, especially in those over 30. I've been fortunate: gotten slammed about and done some epic face-plants (resulting in a memento just below the bridge of my nose), but no structural damage. I owe part of that to luck, part to growing pickier about waves as I've aged, part to stretching, part to understanding the ocean.
Mostly luck though.
I reckon board surfing is much harder. Or at any rate, you can get much better at it; there's so much more one can do. However, you're probably at more risk in a six-foot curl without a board than with. OTOH, a board will get you out into much bigger water, so the risk factor can go sky-high.