Metz 44 AF-1 vs Nissin Di622 II for D90?

Metz 44 AF-1 vs Nissin Di622 II for D90

i'd like to get user info on these two flashguns, please. i have an sb-600 and an sb-24, but both are not functioning perfectly at the moment (sb-24 buttons don't work all the time; sb-600 doesn't fire at all—might be a capacitor or other electronics issue).

i've been looking at the nissin, but came across the metz and realized its functions (and limitations) suit my needs and usage just fine. however, i couldn't find any information on whether it does high speed sync on the d90. for that matter, does the nissin do hss?

any comments on reliability, build quality, exposure consistency, etc from owners would be greatly appreciated. i'm going on a trip this weekend and hope to get the flash tomorrow. i'll be comparing both flashes side-by-side before i decide, but wanted to get as much info as i could beforehand.

thanks!