My OH has an evod, which seems to be a stronger vape even though the coil had the same resistance when we looked. I had thought it might be a different one at first.
When you looked at the resistance did you look at the resistance printed on the coil, or did you test it with an ohm meter?
What's printed on the head can vary +/- about 10% in each direction. Coils for protanks etc are produced in their thousands in chinese factories and there's a little bit of variability between coils. If you use a n other make rather than a genuine coil they can vary more than 10% sometimes. A little bit of difference in the coil can make a large difference in the vape you get.
Without getting into ohms law and looking things up in tables a 1.8 ohm coil on a 3.7 volt battery gives you a vape at 7.6 watts. (most peoples sweet spot is around here) whereas a 1.8ohm coil that's actually 2ohms gives you a 6.8watt vape that would be noticably weaker.
Better batteries do not produce better vapes in principle. A battery is a battery is a battery. And 3.7 volts is the same no matter what battery provides it. (better quality batteries will produce the advertised power rating for longer, without battery sag, so this isn't strictly true but close enough for our purposes here)
What really makes a difference is the electronics regulating the battery supply to the atomiser.
Being able to fine tune the power getting to the atomiser makes a BIG difference. Even something as basic as an eGo Twist rather than a standard eGo gives you much more control about how your vape is much more easily. All you do with a Twist is set it a little lower than you think you need, take a draw and adjust until it vapes how you prefer.
The next step up from that is VV mod, of which there are lots of shapes and sizes. Those allow you to adjust the voltage too, usually via buttons and a screen, they do the same thing that a VV eGo does basically.
The next step up again is a VW mod. These have built in ohm meters that allow you to check the actual resistance of whatever coil is attached and they automatically set the voltage for you depending on what power setting you choose.
The difference in the pricing accounts for the difference in build quality and also the difference in quality of electronics that regulate the power supply.
A DNA mod or a ProVari are mostly lots more expensive than a Vamo or an MVP because the quality of electronics in the device is that much better.
If you're using an eGo that you can't adjust then I'd definitely recommend a variable something. It makes a huge difference in the quality of your vape. Almost as big a difference as using an eGo is compared to a cig-a-like.
If you can afford the jump to a VW mod then go with one of those rather than a VV eGo as they are much better (being able to check the resistance of your attached coil is *really* useful)
