Daley no longer is the pure PP specialist people expected him to be. He's a solid, two-way second pairing defenseman. His defensive game has developed alot, that's his main priority, his offense will come. He hasn't gotten many PP oppertunities yet, but he will eventually. I've not seen enough of Ehrhoff to make a fair judgement, but what I've seen didn't look too good. I believe Shark fans have been dissapointed with him as well.
Daley is the safer bet for now, and probably for the future, even though I'm biased.