from the point of view of reliability — Yes, better external hardware RAID controller from any known vendor. but better to take a couple — so if one dies, be able to raise the array and not wait until you arrive replacement. Programmniy in this respect more flexible, the screws can always put in another machine and build it there.
from the performance point of view — the difference is usually invisible — the modern processors are pretty fast I think.
another argument in favor of hardware — if one of the screws dies, then the hardware he's usually calm vylivaetsya from the array. but the software the options are I had a case where one screw from the burnt electronics has introduced the core in such a reverie that I had to extinguish the machine. ie hot swap hardware is much better (if the controller supports and the basket is)
