I find the opposite to be true. With my mech mods (1 real, 5 clones), I find I constantly have to fiddle with tightening tubes, tightening fire buttons that come unscrewed a little bit (mainly because I want them lined up with no threads showing, but they sometimes won't fire it too loose), opening it up and elongating the battery pin so the battery doesn't rattle (especially when I change batteries - even to the same exact size/model), open it up again to adjust the center pin from the back side so it works on the tank I just put on it, adjusting the tank itself so it makes contact...really a pain in the ....
Most of my mech's have as parts: end button itself, end-cap, 1-3 battery tubes, adjustable center pin (from the backside), top cap...way more parts than my VV's. And don't even get me started on getting the friggin Kick 2 to work in some of these devices when I want to run them regulated...
With my VV mods (like my MVP or VV) it's a single part with nothing to come off it, come loose, and nothing to adjust/fine-tune on the device itself. I simply press the fire button and it works. Worst case (and only on my Kayfun's), and only sometimes, I have to take a fingernail and extend the screw on the bottom of the Kayfun to get a connection. YMMV.
But what am I using right now? A mechanical because it looks cool