I have a 40 watt Weller iron and a 100/140 watt Weller gun.
Basically, I now only use the iron if I need a smaller tip for rejoining wires to circuit boards. If joining 26 awg wire i still bust out the bigger gun.
I do not like just leaving the weller iron plugged in, nor waiting for it to reheat, and if already hot with a nicely tinned tip, it still takes longer than I like before solder starts flowing and there is more risk of melting wire insulation.
With my 140 watt weller, I mistakenly bought replacement tips for the 400 watt gun which are much larger. I filed the tangs to fit my smaller gun, and yes it does take a few seconds longer to get hot enough to melt solder, but I find it to perform much better having more thermal mass and with more surface area, able to transfer the heat better requiring less time.
I was going through the standard 100/140 tips quickly, but am still on the original 400 watt tip, and it shows no signs of abrasion/pitting/ wear.
With the generally short run times of a soldering iron, I do not seem much point in trying to go 12v DC to save some battery power. The 12v options would only be needed for somebody without an inverter and it sounds like they can't do the job anyway. I'll never know for sure as i doubt a 12v soldering iron and I will ever cross paths.