I just did all this research!
I actually am getting both, as I'm in the middle of a long-term round-the-world trip and want all the needles I might need with me in as little space as possible. So everyone thought an interchangeable set would be ideal for me.
I want to do a lot of lace work in the future, and everyone recommended getting wood for that, since control over the yarn is crucial over speed with lace work, plus the Harmony tips are very sharp, which help with the tiny threads (it'll be interesting to see how long it takes me not to split yarn, though).
However, I also plan to do a lot of regular knitting and really like metal needles for that, and I love the Addi needles. Everyone who uses them told me that the Nickel plated Options are the most like Addi, so that pretty much sold me. (If I had an unlimited amount of money, I'd have probably gotten the Addi Click set to see which I preferred, but unfortunately, my gravy days aren't here quite yet!
The nice thing, of course, is that they're interchangeable, so you can just buy one set that fits your general plans for your knitting, and then add tips of the other sort as you need them. If I wasn't traveling, I probably would have gotten the nickel and just ordered the wood tips as I needed them rather than gotten two full sets, which just about killed my wallet.
I did get some Lantern Moon rosewood needles, just because I couldn't resist them. They're beautiful to knit with, in the limited amount of knitting I've done with them so far.
HTH! I'll add that I'm still a relative beginner, so this is from limited personal experience, but I'm trusting that the advice I've been given on the forum here will hold for me.