Good review as usual. But his complaint with the 1.5 DC cartos just highlights a broader subject. Just like voltage isn't everything, wattage isn't everything either. Many atties/cartos will be optimal around 9.5 watts, but others, because of mysterious internals factors, are optimal higher or lower, e.g. the clear Turbo eGo cartos are 3 ohm devices that amazingly seem to work very well on an eGo battery, and are optimal around 5 watts. A Kick set to 9.5 watts would feed it 5+ volts and blow the coil. At least in the XL, it's not that hard to get at the pot to adjust it, though it's facing the wrong way. It just goes to show, there will always be more stuff to buy, and wait by the mailbox for ;-)
that is amazing... yes, another example that baffles me is: the SR 901 atty is around 2.8 to 3.1 Ohm, yet does well with low voltage and IS designed for lower voltage ( i use them from 3.4 to 4.2v).
The 510 SR is 2.2 to 2.6 or so and requires at least low voltage and sometimes more.