A basic question about warp scheduler

Hi, all

I wish to have your kindly help on following question.

In the whitepaper of Kepler GK110, it says that the scheduler is quad issue. My question is:

for the following two grid/block settings, which one is better for such a scheduler:

1). grid {256, 0, 0}, block {32, 0, 0} //scheduler choose four warps from 4 different blocks on same SM.
2). grid {64, 0, 0}, block[128, 0, 0] //scheduler might have more chance to select multiple warps form same block.

Thank you very much for reading my question.