I have a BB, SB and an Omega (BB - 14500/CR2s, SB and Omega 18650/CR123As).
Right up until recently I have been doing 6v exclusively. Mainly 901s and mostly KR808D1 cartomizers. Direct dripping with the atomizers and using cartomizers most of the time. 901s and the KR808D1s because they were running right at 3.0ohms or a bit more. Less than 3.0 ohms and it trips the circuit on the protected CR2s in the BB. The Cr123As aren't so sensitive and Joye 510's at 2.2 ohms work fine, but don't last more than a day or two. I'd say dripping on a 901 at 6v is about ideal but can't justify the overhead and inconvenience. I do 100%VG and very heavy flavors at 26-36 mg. DK-TAB is my everyday. I've tried all the LR stuff at 3.7 and it didn't cut it. Then... for about a month now I've been doing the Joye 510 cartomizers and Joye 510 Mega cartomizers at 3.7v. Amazing. Actually something that works for me at 3.7v. The regulars are ideal but don't last very long (and I'm not thrilled with the shape and you can't fit a regular drip tip on them). The megas/eGos last longer but are a bit too airy of a draw and tend to leak a bit right after you first fill them. Fine after that. I carry the PV in a battery belt holster when golfing and end up grabbing the pv by the tip. Some of the big ones have a tendency to come apart at the connector (they sort off snap back together though -- haha, they should have used glue). I tend to vape everything dry and always burned up the insides of the KR808D1s. The Joye 510 carto filler seems to be burn proof so far. That's where we're at. Oh, by the way, I can do as much vapor with a 1/2 second draw as Bad did with his 1 second draw...