I have always used the e-pen but recently purchased the e-tank. Basically because the liquid comes in a 6mg and the lowest the e-pen comes is 12mg which is a bit strong for me now. the e-tank is a really smooth draw and very easy to fill thanks to the clever people a Vype making the nozzle on the bottle so thin. I've used other types of tank devices and never got on with them very well. but this is perfect. i still use my e-pen when travelling as the no mess change of tips is great.