I will give this a shot as this was a very confusing topic for me when I first started vaping, I bought things that I shouldn't have without knowing exactly how they affected my vaping experience.
It all comes down to wattage. Watts is heat and with different amounts of heat your liquid will vaporize differently. The reason you are seeing conflicting information is because your heat (watts) can vary with different combinations of hardware and there is a range threshold that most people typically shot for to achieve "optimal" performance (flavor, vapor production, vapor warmth, TH, etc). Most feel that between 8-10w is optimal.
So how do you control watts? By adjusting volts and ohms (resistance) with different hardware. Here is a chart that lists voltages and atomizer resistances, both are used to calculate watts.
http://www.e-cigarette-forum.com/forum/modders-forum/71422-atomizer-battery-watts-chart.html
So just raising volts may not get you the desired results. For an example, lets say you have a standard 510 atomizer. Here are some numbers based on a standard 510 atomizer at different voltages:
Standard joye atty (2.3Ω - 2.5Ω)
3.7V=5.95w
5V=10.9w
6V=15.7w
7.4V=23.8w
At true 3.7v (most off the shelf pen and mini style ecigs do not run at true 3.7v and will lower watts even further, see here for more information:
http://www.e-cigarette-forum.com/forum/joye-510/65055-battery-voltages-surprise.html), is well below the 8-10w sweet spot and at 6v you are well above it. However at 5v, its right on the mark and this is why lots of people felt that 5v is where they preferred to vape.
However, in addition to adjusting volts, we can also control ohms, this can be done by using different resistance atomizers. So here are some other numbers using HV (high voltage) atomizers that have higher resistance than the standard 510. You can commonly find 4.5Ω and 5.2Ω resistors, here are some 4.5 numbers.
4.5Ω HV atty
3.7V=3.04
5V=5.6w
6V=8w
7.4V=12.2w
Now 3.7v is far below the 8-10w threshold and 5v is now just above the watts as a 3.7v with a standard atomizer, however 6v is now within the threshold. So what is all this hype about Low resistance atomizers? Well here are the numbers:
1.5Ω LR atty
3.1V(torneGo) =6.4W
3.7V=9.1W
5V=16.7W
6V=24W
7.4V=36.5W
With those you can get to the 8-10w range but do so at 3.7v. Infact it puts you slightly higher in watts versus a 6v setup with a HV atomizer.
Please keep in mind that I did not come up with the sweet spot range and have only followed what more experienced people have recommended and by doing so, it has greatly improved my vaping experience.
Hope this helps, I know if I understood this more when I first started that I probably could of saved lots of money as I bought backup atomizers, batteries, etc. that I rarely use now.