I have a theory based on my own usage...
The 801 pen doesn't give as great a throat hit - the
vape is smoother.
The 901 I have kicks like a mule...
I'm using the same liquid in both... the difference???
The 901 has 1 hole for ventilation in the atom, the 801 has 4...
More airflow=more dilute vapor=less throat hit. Not E=MC
2, but brilliant just the same.