First of all, displayed MHs does not correlate directly to the number of valid shares that are submitted to a pool, just like there is no exact amount of work (hashing) required to find a block. They are both based upon probability where a certain hash-rate will "on average" solve a certain number of shares.
What I mean is the MHs readings are correct in that your hardware is looking for solutions at that rate, but there is also a element of luck involved. A certain hash-rate has a certain probability of guessing the correct hash for a share submission that is accepted by the pool, but there is not a set amount of hashes that correspond directly to one share. So you may get periods of luck where your hardware guesses more than its statistical probability and periods where it does not.
Now as far as your question, I have also noticed that Claymore seems to report a bit higher hashrate than other miners do with the same end result at the pools. I am not sure if it is intentional or just a different way of estimating the hash-rates, but in the end you have already noticed what you should be paying attention to, which is the submitted share rate on your pool. Myself, I don't care if my local displayed rate is showing 10 MHs as long as I am getting the equivalent (or more) shares on the pool than I do with a competing miner.
An analogy I have used before is look at it the same way you look at your car's speedometer. You may have aftermarket tires that throws the calibration off one way or another. The speedometer is still useful for driving as you can adjust your speed up or down, but the real world speed is determined by the radar gun. If you go to fast, regardless of what your speedometer indicates, you will get pulled over.
Put another way, if my speedometer is 4 mpg faster than yours and we are driving along together on the expressway, we might stay next to each other even though I show I am going 69 and you show your are doing 65 exactly. So going back to mining, while the locally displayed hash-rate is useful for tuning your miner with settings and clocks to get better performance, it is the real world share submission at the pool that you should worry the most about.