Maybe the issue Stacy is trying to make is that in your own sign shop... colors, output, fonts, profiles, etc are easier to master. But when you are accepting files from customers then you run into trouble. Many years ago, I mostly used Corel and after getting burned on bad output from Corel I switched to Illustrator and have never given Corel another chance.
Keep in mind that I AFAIK, eps is Adobe's baby so you will usually get predictable output when that eps file is opened/manipulated in Illustrator/Photoshop. Flexi or Corel may be superior in one way or another, but outside the confines of your shop EPS and Ai files are the standard
If you take your Corel or Flexi files somewhere for output you will be turned away or laughed at. Mac/Adobe are still very much the preferred pairing when you go "outside" of your shop. Not that long ago, some shops laughed at you when you brought in Indesign files. Quark was the standard for desktop publishing just a short time ago
Anymore you cannot usually tell if a file was created on a Mac or PC and I won't argue the point. I have used both and they have their strengths/weaknesses