It's a matter of choice. Dry rock has it's advantages (usually cheaper to aquire, no bad hitchhikers, no vegetation to die off, etc.) but also it's disadvantages (looks WAY different than what you already have, no good hitchhikers, etc.). Live rock will probably look closer to what you already have and would probably have a bacteria colony already growing plus you could have some cool (or bad) additions to your tank. Decide what you would prefer and go with it. There really is no totally right or totally wrong answer.
Whatever you use, be sure to rinse it well to remove any dust or debris from the rock.
Why do I love fish? Because every time I stare into the little world I have created for them, every problem I have just floats away....