Hi Folk,
Just thought I would chime in here and relate the differences I have discovered. I have been vaping for about three months and have tried products from LeCig, Vapor 4 Life and Green Smoke.
First, the leCig D-2 and Green Smoke cartomizers do have the same threads and they are interchangeable in that respect. In fact, the LeCig D-2 cartos will work with the Green Smoke batteries. However, without modifications, the Green Smoke cartos will not work on the LeCig USB pass-through (or batteries if they are identical to the pass-through). The problem lies in the way the two systems have the air vents designed. The LeCig D-2 cartos have notches in their cartos to allow air flow. The Green Smoke cartos have no air vents and are pretty much air tight where they connect to the battery. The Green Smokes air vents are located at the tip of the battery by the LED. There, clear as mud?
There is a quick and easy work-around to get the Green Smoke cartos working on the LeCig USB pass-through (and batteries?). I just pulled out the old Dremel and cut a few small notches at the base of the carto. Instant air vents! Worked very well.
Now, having rambled through that, I'm going to relate my own experience and opinions of the three brands. The may differ widely from yours.
The Green Smokes do produce superior vapor. BY FAR! I don't know how or why, they just do. But, they are just too smooth for me. Minimal throat hit and, as I'm trying to replicate the analog experience, they just didn't work for me. Also, nasty, burned paper taste about halfway through the carts.
The LeCigs produced less vapor but slightly stronger throat hit. But not enough to feel like the "real thing" for me. They also suffered from the burned paper taste about halfway through the carto. Bleh!
The Vapor 4 Life has been a totally different experience. Particularly with the newer "Premium" cartos which are a mix of VG (vegetable glycerin) and PG (propylene glycol). The vapor is ok. Not as good as Green Smoke but very acceptable. But, WOW! The throat hit is second to none. In fact, it may take you back to the day of your first analog. The upside is that you don't have to "puff-puff-puff-puff" in search of the "hit" and the smaller, single puffs make the cartos last longer without slamming into the "burned paper flavor" wall. And, the flavors are really nice.
So, I hope this rambling treatise is useful to someone. It's 0200 and I'm running on empty. I've basically quit trying to quit the nicotine addiction but really want to get away from tobacco use. I think the e-cigs may be the best hope for that. I'm not totally off the tobacco but I am down to about 3-4 analogs a day.
Anyway, best wishes and success to you all,
Jim