^^^
Both, Lol
I'm moving away from flash these days, but in my short time in photography I'v tried pretty much most flashes from Canon, Nikon, Nissin, Yongnuo and IMO the Di866 is a very good flash, but compared to some others, it has a longer flash duration than say the Canon equivalent. As for Nikon, the SB-700 and Di866 probably has a similar flash duration with the SB-700 being a smidge quicker (better x-sync).
The only times I found my self over heating flashes like the Di866, is outside at full power and often (but not only) with HSS trying to take on the sun, inside you just don't need to be at full power, unless in a very large or dark church maybe.
Canon flashes (580exii/430exii) let you fire off allot more pops before the thermal protection kicks in, and the SB-700 is impossible to overheat as well similar to the Canons as it just slows down the recycle time.
If I remember correctly it only took about 10-15 consecutive full power pops for the Di866 thermal protection to kick in (I may have been using a battery pack due to long recycle times, not sure though as it was quite along time ago).
In every other respect though, I found the Di866 was an excellent flash.