i think there are a couple of things to consider before making the decision.
1. How comfortable are you with buying rock from a reef that has been destroyed so you can have it in your house?
2. How much of a perfectionist are you about your rock scape?
3. Are you willing to assume the risk of the unwanted hitch hikers that sometimes come with live rock?
4. Do you care how long it would take to seed dry rock?
For me #2 was the concern so I opted for dry rock that i could make how i wanted before hand. Then i bought (1) piece of live rock from the LFS popped it in the tank to get the seed going.
Now it all looks like that first rock even though that piece of live rock is now dry rock in a bucket. I guess it's up to you, i like the dry rock method it's a lot cheaper and i didn't feel bad about busting it when "designing" the scape.
Good luck, there really isn't a preferred or wrong way to do it...you just need to make sure you get out of it what you want.