Software RAID efficiency: Disks vs partitions

Hi,

Need some advice. I am being told by a hardware person that
a software RAID (Linux mdadm) array should use disks instead
of partitions for much improved efficiency. For the life of me, I
cannot see why this would be the case, and searching Google
turns up no such evidence. On the other hand, the difference in
wasted space would be huge, as we are talking about 3TB disks
to be used in a RAID-6 array.

Could someone more familiar with software RAID offer advice?

Regards,
Gora