In the intrest of this question I use both systems daily, both have there good and bad points. However if you are looking for good looks and repairable in the future with parts obtained from your local hadware store, then go with copper.
If you are looking for speed and are not too concerened with looks, as pex is inpossable to keep neet then go with it. However if you do intend to do any repairs and or upgrades to this system, you may have a problem with getting parts and tools to make such repairs, as if you are not certified to install most supply houses will not sell to you.
Also even the simple expation tool used for the installation is about $300.00,
add that to your shopping cart as well.
BJD