Here's my take:
Darwin -- for long battery life, pass through capacity and easy to use variable wattage power. Battery warranty for a year and replaced reasonably. Nothing extra to buy but juice and atty/carto. Some don't like it with tanks....some do.
Provari -- for one very fine made vaping machine that is also variable volt. You may need to carry a spare battery, depending on your use and style of vaping. Kind of big if you add a tank. It's weight is part of it's charm.
Vmod XL-- one pretty sweet 3.7 volt bottom feeder at a very low price. Best pocket friendly feeder made, imo. 18650 means long lasting battery -- a day or more for most.
the new to be VVPV by the buzz guy --- very new and very interesting. Maybe too new? I don't think you can change the batteries, but it does charge via usb cable....use like a pass thru.
GLV -- good old made in America fine vaping gear and I just can't leave them off the list! Very high on the reliability list, I do believe. There are a few models to choose from.
Super T Manufacturing and Clouds of Vapor also offer very fine mods.
And, yes, most of these will require some kind of wait.
Go for it --- get the mod that most interests you.