Ross,
That's a tough question.
It took us weeks to run coax during initial construction of our new casino building in 2000. We pulled approximately 1,000 lengths of coax to approximately 25 locations, leaving up to 50 feet of spare length rolled up on the cable tray to allow for the final pull lengths. Managing those ends was a royal pain in the butt: we would have to pull the bundle off of the tray and lay it across the floor so that we could separate individual cables and pull them to each camera location, then trim any large excesses and terminate the ends, making certain we replaced the wire number from the original end.
We threw out an awful lot of cable during the trim process and just managing the remaining spares was a pain - each time we added a camera, we would have to unwind the entire bundle to retrieve a new cable. 25-pair (or larger) UTP cabling is much easier to manage - label each backbone cable and the color codes take care of the rest of the management; co-locate punchdown blocks with camera power supplies and there will never be much waste.
On the other hand, we do have occasional issues with bad UTP connections - not often, but obviously more often than we have with coax.
I think we would still run UTP for a large-scale system if a sufficient percentage of the cameras were going to be analog. But I have to wonder if that would be the case. The decision would depend on doing two separate layouts: one using analog plus some IP and the other using all IP.
One thing we would change is our choice of punchdown blocks. We started with 66 blocks and have continued with them for the sake of simplicity and to keep the system the same but I think we would consider using 110 blocks. I would also have to consider whether we would continue using single pairs in a 25-pair cable for video or whether we would lay the system out with 4 pairs per camera to ease the switch to IP.