The point lobro1 makes is very important to understand. "3.7v" batteries as used in big battery PVs charge up to 4.2v and beyond. They also deliver that sort of voltage for the vast majority of the charge (as opposed to normal e-cig 3.7v batteries which drop down very quickly). Therefore the difference between a 3.7v and 5v big battery device may not be as profound as you think.
At one time the most important factor for "mod choice" was the atomiser it came with, but now adapters are readily and cheaply available. I have a SD which came as a 901 device, but I also use it with 801, 510 and 401 attys.
Although I'm an SD user, I think the things you need to consider for any big battery device are: size, shape and button position (all entirely personal choices - I like bottom buttons and have a SuperSix coming), then voltage, then atomiser choice...
At one time the most important factor for "mod choice" was the atomiser it came with, but now adapters are readily and cheaply available. I have a SD which came as a 901 device, but I also use it with 801, 510 and 401 attys.
Although I'm an SD user, I think the things you need to consider for any big battery device are: size, shape and button position (all entirely personal choices - I like bottom buttons and have a SuperSix coming), then voltage, then atomiser choice...