Rachy_B I was having the EXACT same issue this morning. I had two Ego-C setups, with different juice. One tasted awfully burnt, the other tasted great. Visually I couldn't see a difference in the wick between the two. I ordered a couple of new things based on the advice here, but I think I need a crash course in ohms / resistance.
Okay, I'm no expert, but this I what I've learned...
Power is the rate of energy transfer, and its measured in watts. Your coil has a resistance to the flow of electrons through the wire. The amount of resistance to the flow of electrons is measured in ohms. Power can be calculated by this equation:
(Volts x volts)/resistance = power
So, if you have a voltage of 3.4 and a resistance of 2.5, you've got (3.4Vx3.4V)2.5ohms=4.6 Watts
But... If you have variable voltage, and crank your voltage up to 4.2V, then your power will be 7 Watts, with the same resistance coil.
Conversely, if you can't crank your voltage up, you can get a lower resistance coil. So, say you have a 1.8 ohm coil at 3.4V battery you get 6.4 Watts.
You can increase the power, or rate of energy transfer, by either increasing the voltage of your battery, or by decreasing the resistance (ohms) of your coil.
I'm sure that's not super technical, but its sort of the best that I understand it. Increasing power results in a warmer, more kicked up vape. Decreasing power makes a cooler, less powerful vape. There are limits of course, you don't want too much power or your juice will burn. You don't want too low of a resistance because it will suck energy out of the battery too quickly, which can be dangerous if you don't know what you are doing.