The reason is the processor. Different vaporizers function with different efficiencies. Depending on the quality of the unit's processor, your vape will differ.
All vv/vw mods accomplish the vv/vw using a system called Pulse Width Modulation, or PWM. The mod pulses a series of voltages multiple times per second to reach the voltage you set. The speed at which the processor pulses will determine the quality of the vape.
A slower processor, like the Vamo for example will cycle at 33hz per second. The pulsing is quite noticeable at this speed- most users can even hear the pulsing manifested as a "rattlesnake" sound. The provari for example cycles at 800hz/second which is indistinguishable to the user. All other mods fall somewhere in between. The evic cycles at a little over 100hz.
I've read that the innokin products are quite speedy on the cycles as well but I can't recall the results. I do have reason to believe that the newer variations a la the v2 and newer models have quicker processors than the v1s and such.
It's likely that you SID cycles at a higher rate than your MVP v1.
Mechanical mods will give you a straight DC current and does no cycling whatsoever.
Evolv mods and kicks have an extremely efficient processor, on par with the speed of the provari processor. Same thing with the semovar. But the list pretty much stops there. Everything else is noticeably different.
The knockoff kicks like the sigelei kick cycles at 33hz/second- same as the vamo.
I hope that helps explain things for you.
Have fun and vape on