DRi have said that there is a SLIGHT (i.e. measurable in benchmarking but not noticable in the real world) speed improvment using 7200 rpm drives in the pro, for “lesser” drobos there is no difference between 5400 and 7200rpm drives (and conversely for elites there is quite a difference between 5400 and 7200)
WD have had to tighten up their language before they get sued for being misleading, their current GP page says:
Calculates optimum seek speeds to lower power consumption, noise and vibration.
A fine-tuned balance of spin speed, transfer rate and caching algorithms designed to deliver both significant power savings and solid performance. Additionally, WD Caviar Green drives consume less current during startup allowing lower peak loads on systems as they are booted.
you’ll note that the “power” no longer mentions spin speed being variable
intelliseek it simple common sense in that there is no point in whipping the heads over to the correct track if your sector isnt going to come around for 3/4 of a revolution - so it calculates how quickly it has to move the heads so that the head gets to the right track just in time to read the data and doenst waste power getting there too early.