Assuming proper mounting, I'd venture to guess that Scythe Infinty would outperform Ultra-120 by a small bit. It's just from the look of it - 5 heatpipes working like 10, and look at the number of fins and how tight they are. In theory, that should beat the Ultra-120.
having more fins is actually bad, it requires you to have a higher flow fan in order to work properly, having a lower fin count does decrease cooling area, but it allows lower speed fans giving a quieter computer, i personally would rather have a decent oc that was quiet, than a rocket with a couple hundred more mhz.
And if im not mistaken, a heatpipe works by heating one end, having the heat carry over to the other end where the cooling is done, and then going back to be re-heated cycling over and over again.
edit: one more thing about some of these benches on heatsinks, if they dont have the system in a closed case, how can you actually believe the temps they get, they're getting clean cool airflow which isnt possible in a real case situation.