RAID 6 (ADG) vs. RAID 50 (NPG: 2) performance ?

[Server-Support]

Hi people,

Between [b]RAID 50 (NPG: 2)[/b] vs. [b]RAID 6 (ADG)[/b]. Which one is performing better write performance for large backup server repository ?

Here's the current backup server deployment:

HP DL 385 G7 with SmartArray P411 - BBWC present.

HP D2700 StorageWorks Enclosure 1 
LUN1: RAID 50 (NPG: 2)
24x 500 GB SAS 7200 rpm HDD
1x hot spare

HP D2700 StorageWorks Enclosure 2
LUN2: RAID 6 (ADG)
25x 500 GB SAS 7200 rpm HDD
no hot spare

I do not use RAID-5 because it is not recommended by HP for any LUN with 12+ drives.

Thanks in advance.