Yes, the topper and the build you put in it is the clear majority of the difference. It brings the question, what are you looking for? Temp control? Flavor? Clouds?
The idea that mods just produce power to fire a coil...I am rather amazed at my wife's Provari and Kayfun Lite Plus whenever I grab it. The smoothness of the power signal plays a role, too. In the same sense, the Provari (the 2.5 blems at $35) just aren't good for power vaping.
What are you looking for as the end result?