My interest is whether the rate seen at the pool matches the one reported by the miner. As for comparing the two miners, compare the total number of accepted shares at the pool (that's not equivalent to payout because of PPLNS).
Based on the data I have seen so far, none of the two miners matches exactly the pool reported rate. I should see 5.8kH with dstm and close to 6kH with bminer. However, instead, I see 5.4kH and 5.5kH. There is no way to know how different pools/miners count hash rate. Therefore I cannot explain why.
However, the numbers are proportionally in line with each other.
On the pool: bminer is 5.479kH. Dstm is 5.375kH. That's 2% faster.
Miner reports: bminer is 5.99kH, Dstm is 5.810kH. It is close to 3% faster. But consider bminer has 0.5% rejected rate, while dstm has close to 0%. This number makes sense so far.
One thing I observed in the past is that the gap between nanopool number and my ewbf number (I used to run ewbf) is usually closer than the gap between flypool and ewbf. That was another reason why I prefer nano.