Two awesome boards. Great quality construction, light (12'6 around 8,2 kg depending on the volume; 14'0 around 9 kgs depending on the volume), stable and with proven performance.
Both boards perform well in all conditions, with the Blackfish more suitable for someone who paddles more on the ocean and the Whiplash for someone who paddles more in flatwater. But there are people who prefer the Whiplash even on ocean conditions and the Blackfish on flatwater.
You can check Dave Boehne giving a complete explanation on the Whiplash:
and on the Blackfish:
I've ordered the Blackfish 14'0 x 25'' and I will use it mostly on the ocean (beach race and some downwind) but also on some flatwater events. But I wouldnt mind having a Whiplash
Hope it helps!