It depends on on the user, and if they want a cigarette sized/somewhat looking device (510), or as some so nicely put it, 'a crack pipe looking thing, with a button'
Sometimes, they're complementary - use the SD/GG/prodigy/? at home or in car, grab a 510 kit for at work, club/bar, etc.
All of the 'mods' are really nothing 'special.' By that, I'm not taking anything away from them, but they all re-use existing e-cig atomizers, and are simply a power source mod, although usually part of that is *much* cheaper replacement batteries. When it's said and done, they do one of 3 things.
1. Provide a manual switch, which you may or may not have had before, depending on the atty used on the 'mod.'
2. Always provide longer battery run-time, from the JS at 380mAh (around double, or at least 100mAh longer than a KR808D1 battery..but also provides a USB passthrough for charging in place, which is nice), to up to ~1000mAh and up. This also provides 'new battery consistency' for a much longer period, but at the same voltage, from a fresh charged good battery, shouldn't be a significant change for the first few hits, until the original e-cig battery starts discharging..consistency is nice, as is battery runtime.
3. Some increase voltage as well. Higher voltage in general = uses more juice, produces more vapor, *may* result in shorter atomizer life. Some report flavor loss at higher voltages, and others report *better* atomizer life (likely due to burning up ot the deposits). Likely depends on the combination of voltage *and* atty - I think some work better at higher voltage than others. No one knows if any of the inhaled or exhaled vapor's ingredients are altered at higher voltages (such as acrolein production, etc).
I think if GG had a 5v model, I'd be all over it, myself. Am looking at the Prodigy as well, and JS v2 and the Cameo when it comes out. The greatlakes vapor new device looks interesting as well.
