If you work at diff 32 and send a result to the pool, it will have value '32'. If you work at diff 128, each result has value '128'.
At the end of the round, those values make up your share of the reward proportionally.
If your diff is so high you miss to send result across a whole round you'll most likely be screwed somehow. Pools don't reward share value exactly and the time distribution is important. Producing less than 2-3 results per minute might incur in quite some loss, especially if your pool has high rej% such as the case for p2pool.