cfr
Black Belt
I do as you mentioned know that possibility of an injury rising dramitically using a closed hand, but the power of the closed hand negates that portion for me personally.
I was of that thinking as well, until I really spent some time developing my open hand striking. Now that I've gotten used too them, my power is far better open hand than closed. I think the reasoning is:
1) My arm is more relaxed.
2) I am less worried about injuries.
This has just been my experience, but now that I stike open handed full time I doubt I will never go back to closed.