I have had a regular Provari that got 90% of my vaping attention, just because it was the most consistant and dependable mod I have, and just feels the best vaping experience. I bought two inexpensive V-V gripper-style mods to use for out-of-the-house vaping yet still grabbed for the Provari when going out the door.
I recently got a Mini Provari for the above. Because it is lighter and more pocket-friendly and still gives that Provari vape experience, it gets to see the world and I continue to use the larger Provari at home.

___
Concerning backup mods, having a backup that uses the same battery as your primary battery device can be an extreme plus. All of my current mods use either the 18650 IMR or 18350 IMR; it's just easier to keep the sizes of batteries down to one or two different sizes for the charger configurations.
Three of the mods use the 18350 size and three use the 18650 size. Only my Altsmoke BB uses a different battery (14500) and it doesn't see much use.
____
Having a mechanical mod as a backup can be an advantage for a couple of reasons. Number one: dependability. If the zombie apocalypse or FDA deeming regulations happen to occur, you're set. Two: should you decide to get into a rebuildable atomizer at some point, a mech mod is what most people seem to settle on with them.
I have a Silver Bullet which I feel is a great mechanical. It and my BB were my first mods. The SB shares the same 18650 battery that I use with the Provari and one of the V-V gripper mods.

Silver Bullet with an AGA T2 rebuildable pyrex tank.