I think if you're going to have an raised floor environment then overhead cabling makes a better compliment because you won't have horizontal cabling constricting airflow. But I also think that plenums and duct work is vital as well for even distribution.
Leaving options open is a good thing as well. Most data centers I'm seeing nowadays is going with the overhead system because it's cheaper, but then at the same time they're deploying overhead horizontal cabling.
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