Arbor vs Narus comparison?

[andy lam <anwalam () yahoo com>]

Recently I've been searching for something that is comparable to Arbor to see what else is out there.  Someone 
suggested Narus.
 
Anyone out there have an opinion regarding the 2 applications and their differences?  Or another application that is 
worth noting?
 
I am currently using Arbor Peakflow for Netflow analysis against my peering/transit traffic and their Security suite to 
identify DoS, etc at the edge.
 
Feel free to contact off-list.
 
Thanks