The pool hash rate is an estimate, whereas the client hash rate is your GPU's hash rate.
Do you actually mean a different measure and not hash rate?
well, I mean hash rate but measured in a way so that it makes sense to fine tune.
For example if you start several miners on one gpu you might get a higher hash rate reportet from the miner instances alltogether but because the stale shares increase it might be less efficient.
So I guess it's miner hash rate in most cases and pool hashrate to check including influence of stales and network.