This one used to be accurate, whereas the others had inflated numbers. But now they all have similar numbers so I'm thinking this one needs a little tweaking. You can see BChydro's explanation why his is more accurate a few posts back.
I've been wondering about dwarfpool myself, they may be inflating the numbers, people see a higher hashrate and think this pool is better for me. I've moved some miners to nanopool to test. I like their per rig stats better anyway.