I have the Reuleaux and it is heavier than I thought it would be and doesn't fit in your pocket as well as a flatter mod. You get the full 200W and battery life is amazing. The build quality of both is going to be the same I would say, the releaux feels really well made, I had an Esquare and that was made well too. If your happy with 133W and lesser battery life then the Efusion is going to be easier to live with, it will be lighter and its form factor will fit in the pocket better, plus it's cheaper to buy and cheaper to buy new batteries for it. If you want the longer battery life, have bigger pockets and don't mind the extra weight and want to have the extra wattage then the reuleaux is amazing. For my lifestyle either are good mods for me and both are better than any mod that uses a lipo as I don't like charging stuff when I am asleep the only way I could live with a lipo version is to have two of them, even then charging them would be a pain. Just to be clear though, I am very very happy with the Reuleaux, just trying to be subjective. The Reuleaux is in stock in the Uk from totally wicked at the moment btw, that's where I got mine from. Hmm also the Reuleaux feels really good in the hand due to the shape, and I don't think its possible to make a 3x18650 mod any smaller. Rob