It's all about Watts. Watts controls the heat produced by the coil. Watts is what determines your flavor. Thus when discussing resistance and volts, you have to keep Watts in mind. Voltage and Resistance affect taste but only to the point that it affects the watts seen at the coil.
According to Ohms Law, Watts = (volts * volts)/ohms
To achieve a desired wattage, on lower ohm atty's you need less volts. On higher ohms atty's you need more volts.
Lets look at Protank 2 with a 1.5 ohm head with a Protank 2 with a 2.5 ohm head. Assume you want to drive 7.0 watts to get your desired flavor.
On the 1.5 head, you would need to drive the atty at 3.24 volts with an amperage 2.16 amps.
On the 2.5 head, you would need to drive the atty at 4.18 volts but with an amperage of 1.67 amps.
Now with a fixed voltage battery with like an eGo-T, you have no choice but to run that atty with a lower resistance head. And as a result, with the higher amp draw, your standard eGo-T is going to drain faster.
With a variable voltage battery, you can run the battery at 4.1 volts, and thus lower your current draw by nearly 500ma
The other advantage of a higher ohm coil is that it's contains more "material". It is going to handle the same wattage much easier and therefore last longer.
Personally, I think the use of lower resistance heads were the first attempts of vapers to draw more flavor from their
batteries. Back before Variable Voltage
batteries, coil resistance was the ONLY thing you could control, since standard Li-Ion batteries gave out 3.7 volts.
With the advent of variable voltage batteries, you can now up the voltage output of the battery, this allows you to use a higher resistance coil which will last longer as it is passing less current
Regardless of the route you choose and the hardware you have, It's all about the Watts.
For a fixed voltage battery, you have no choice but to lower the resistance.
If you have a Variable Voltage Battery, I think higher resistance is the way to go. Your heads will last longer.
