Where are you racing?
You need to consider more than just what people say is faster. What really matters is what will be faster for you… That comes down to tuning support, do you have someone on hand to get the absolute maximum out of your engine? Any amount you gain will depend on being able to tune the engine to that level. The track layout can play a part too on which engine has the upper hand.
Another thing to consider is that over the years I’ve seen claims of “new thing being faster than the old thing” and it’s rarely backed up with laptimes season over season (All other things being equal). The differences tend to be very subtle.
I’ve out qualified KZ10’s with a K9A that was supposedly “too old”.
Blanken are certainly a top tuner, no doubt about it… but will they be the best choice for you, you’ll have to decide.