As an observation, you have been on Signs101 for 9 years,
what have you been using the whole time?
Do you design more than signs?
Are you self taught in design software?
If it's Signlab, and you have not learned it yet, I would
think any software where you can get online or classroom
setting would be best. I'm thinking Illustrator (or Corel) have
an edge on Signlab (or any sign software for that matter)
I started as a traditional graphic designer (pre-computer)
and taught myself software, but watching fellow designers
fly through Illustrator (or Corel) can speed up your skills very
fast.
We use Illustrator because we just design and only design... it
works with any format we need, it will easily import into any
sign software, it also works better with our workflow as we also use
Photoshop and InDesign.