Yep I like the 901 for stealth smoking, in malls, restaurants, theaters, etc. cuz it's small & can be concealed in your hand, then blow the vapor into your hand or down yer shirt. Drawback to the 901 is small carts, gotta refill every couple hours & recharge batterys often. Mine came with batterys charged enough to smoke while fully recharging the second battery.
The Penstyle is a couple inches longer & larger diameter tube, carts hold more e-
juice & batterys last longer so I use it more than the 901, driving, home, on the computer, watching TV, etc.
It was easy for me to quit tobacco on the first day, but I still get occasional cravings & will smoke 1 or 2 a day sometimes, morning & night. A far cry from the 50 real cigs to only 2 a day though. After 2 days my coughing went to zero, and energy climbed quite a lot. I can smell things I had forgot about. I was in the grocery the other day wondering what the awful smell was in the aisle I was walking down & realized it was coming from another customer, that ' smoke smell ' coming from his clothes, lol.