I have run with a pack most days for the past 10 years and have tried many brands (REI, Osprey, Berghaus, Golite, others). The Terra Nova Laser 20 is the least durable pack I've ever had. Pack failed with a broken zipper after 3 months of use. Since the zipper runs the length of the pack if you have a zipper problem your pack is basically useless. Customer service from Terra-Nova was unresponsive and unaccommodating.
ccchansI haven't used either of these but have run ultras with the smaller volume vest-style packs from Nathan and Ultimate Direction. My current favorite is the UD Scott Jurek model - very light, comfortable, and I like the 2 collapsible bottles up front vs. carrying a traditional hydration bladder. The big question with these packs would be how stable they are with a heavier load so you might want to try one on first before purchasing.