They are different sounding DACs. And positioned differently.
If you want to have the best all-in-one DACs and headphone amp (the power of DAC-10H is amazing), then DAC-10H is the one. DAC-10 by itself has the clear and detailed sound characteristic of ESS 9018K2M DAC chip. DAC-9 has the warmer AK4490EQ DAC chip. In terms of spec, # of inputs, DAC-10 is better than DAC-9.
But if you like warmer sound, then DAC-9 to you will sound better.
In any case, these are all reference class products.