BobDDuck
Island Bus Driver
If your plan is to go fly big(ger) 121 airplanes some day, then I think time spent in a 1900 at Lakes, even if it is going to be in the right seat for a while, will be more valuable than time spent instructing in light twins. That said, if you can't financially work with what GLA will pay you in the right seat of their planes (or the left seat for that matter), and with the CFII job you can, I would take the teaching position. If I recall you are pretty young and the airlines aren't going anywhere in a hurry and sooner or later another airline, that pays a bit more will offer you the gig.