According to Mark :
but the theory is that if you let it run dry, there is only a small
amount of gas left in the carb, yes that will evaporate and leave a
small amount of residue...

Mixed 2-stroke gas is fairly viscous, and there'll be considerable
residual gas, of which anywhere up to 1/16th of it is goo-forming oil.

Then, with small bore lines and carbs (ie: weed wackers), you could have
gunkification within a few weeks. Especially on things like in-tank
fuel filters where the elements will be saturated with gas no matter
what you do in turns of running dry. Come spring, the elements are plugged.

the alternative is leave the tank full and you then have an unlimited
amount of gas to evaporate leaving a much larger amount of residue...

It takes a very long time even for a (sealed) weed wacker tank to appreciably
evaporate. Meanwhile, the volatiles are keeping the fuel from sludging
up (and stabil would prolong that).

thats why I add Stabil then let it run dry. whatever small amount of
gas is left still prbobaly evaporates but if there should be a large
pool left somplace, the Stabil will slow down the degredation.

Stabil will not slow down evaporation. Once it's evaporated leaving
two-stroke oil behind, stabil won't prevent it from becoming sticky muck.

On the last weedwacking day of the season, I simply stop my stihl and hang
it on the wall. Full of gas. Come spring, it starts in 2 pulls. Just
like it does in the summer when used every week.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.