I tired +7 khal buckler and +7 tirf buckler for niff.
When I used my khal, I died in niff like once every blue moon? *Almost never*
When I used tirf, I could expect to die 2-3 times a day.
I've also heard similar stories from friends who had tried both.
If you want something that will work in alot of diff maps, then go tirf.
But if you're only using it for niff, use khal.