I spent 3 months with the M401 which was my first
ecig and just got a VK KR808D yesterday. After half a day of use I'll say the VK blows the M401 away in terms of convenience,
throat hit, vapor production and taste. Haven't refilled a carto yet, but I can't imagine it's half as much a nightmare as filling a tiny M401 cart. I used one carto last night and it kept going and going. I'm amazed so far.
The only thing I can see the M401 has over the VK is it's smaller size is more like an analog for me.
(I'm comparing manual
batteries for both.)