DSE products, 1st their was the 801 "penstyle" which was one of the first e-cig with a heated coil. It was somewhat of a copy of the Ryuan ultrasonic unit, the original e-cigarette. But didn't work and cost a fortune.
The 901 came out after the 801. It was designed to be a mini, because people didn't want a pen size 801. The 901 atomizer design changed from the leaky 801, where the battery fit inside the atomizer, so
juice could make is way all over the battery, to the common atomizer (501 style) of today.
The DSE 901 was challenged by Joye's offering the 510. The 510 what smaller, produced more vapor, but it was a bit harsher and with less battery life. 510's started to beat the 901, giving the market advantage to Joye.
DSE came out with a mod/kind of predecessor to the ego, the 905. It was a piece of junk, which would melt down on its own with its "cleaning cycle" and the button never worked. They kept making revisions to it V1, V2 V3 (lost count and didn't care after that) but there was always a problem. DSE never recovered, hasn't made a decent offering since the 901 and has faded to Joye.
Joye went on to make its own 801 cone (302) and 901 clone (??) these products I believe sell better than the DSE originals, putting another nail in the DSE coffin.
The M401 is a Smoore product. Was popular around late 2008 early 2009. Was small, well build, very tasty vapor, but with a small leaky cart. This model went on to become the 601 and the basis for many "branded" products like revolver. In my view the 601 was the same thing with a different threat. Smoore didn't develop any new products. 401/601 popularity has faded.
Joye introduced the eGO in mid 2009. Was a smart move using the 510 atomizer with a cone. Changed the characteristics without changing the parts. Popularity went through the roof with its relatively small size offering enough power to last almost as long as the big mods.. From there the eGO got is own eGo atomizer in Summer 2009, and the eGO-T (
tank) in 2011.