if RAID 5 - multiple spares. RAID 10 will have better read performance - 2x over RAID5.
Also, are these local disk arrays of is this SAN storage. This is important since different SAN HW performs differently.
Take EMC VMAX - it's best performance is all RAID 5 - in 3 disk RAID 5 arrays virtualized to the hilt.
This was a surprise when we benchmarked it between its best practice of the RAID 5 in a 3 disk arrays over all RAID 10 of various sizes.
I've also done various IBM SANS and SVC storage as well basing tests on RAID 5 vs RAID 10.