Highly recommend building it. You can pick all the parts you want and will then really know the rifle inside and out. It's fairly easy if you are at all mechanically inclined and only requires a small amount of specialized tools.
Whichever path you choose I would highly recommend that you first read the stickies in the AR15 section, especially AgentTikki's Primer!!! Then you'll have a better understanding of what kind of AR would best suit your needs.
I built my first one in July, just completed a 2nd and have 3 stripped lowers in the safe waiting for attention. They multiply when you're not looking.
On second thought, if you want to avoid BRD, which is highly contagious and not covered by insurance, forget you even started this thread.
Also browse around the AR setion here and the AR15.com forum for lot's of info on brands, dealers, and building your own.