I've owned a C7 Z06 for 4 years come spring and I have a 5BW thats at 4D00 status, I will be keeping both.
They both have merits and I guess it really depends what you want out of your LT4 powered dream machine. One is a sports car the other is a sedan. Yes the Blackwing drives amazingly well but its still a large sedan, the Z06 is a low riding sports car, do these things matter to you?
The interior and tech is obviously superior in the Blackwing, the C7 interior is quite old looking, however certain spec'd interiors can make it feel decent but its still not on the level of a Blackwing.
Sure on paper and for the street the Blackwing sounds like the win, its nicer, has similar power, can fit 4 people, the Z06 might have issues scraping in certain parking lots and it may be a bit more of a pain to live with because of that vs a Blackwing.
However I love my Z06, I drive it all the time, I love driving in a low seating position, the Z06 gets more attention, its a Corvette after all, maybe thats a good thing or maybe not but I always like the thumbs up and kids jumping for joy when they see it, the Blackwing looks an awful lot like a regular CT5 and blends in much more.
Honestly its a tough choice, at least for me, which is why I'm keeping both. If I had to pick one, I don't know if I could. I'd probably still find a way to own both.