I usually go for innovation because it is cheaper. Honestly, what is even better than ING2 is to stretch your craft out longer and get more touches. One more successful touch will net you more benefit than either of those skills will. I used to try to save enough cp out to do ing2 and inn. Now I make sure I have enough for gs, bb, and sh, and will take chances purchasing durability for more touches. If I get some good conditions and have enough for inn and ing2, great. If not, I'm better off finishing at 10 stacks without them than at 8 stacks with them.