Size, power, material, cost, technology- including but not limited to lack of wires, heat up time, heat exchange, magnetic charging cable- convenience, versatility- if they bring out the oils front end and water pipe adapter-lifetime warranty-if they stay in business- a lot of these things are conditional on whether or not their claims are substantiated and on whether or not it has durability because, if they have to fill a ton of warranty claims in the first year, I would think they would have a hard time keeping the business in the black. I may have missed a few but those are the reasons I can think of.
edit: also because Conrad played a sick uke in the campaign video!:-P Plus not all 136 pages is on topic, we got bored and took the scenic route part way through.
Edit: I forgot the best part... It clicks like a real frickin pen!! Whaaaat?!