cryptonight = 450 vs 690
neoscrypt = 500 vs 1000

So
if you run Cryptonight hashing, the four 1070 cards will produce 900 more hashes vs six 1060 cards
if you run Neoscrypt hashing, the four 1070 cards will produce 1000 more hashes vs six 1060 cards

So yes, its better to run four 1070 ti cards than six 1060 cards!!!!!