I've been using both CorelDRAW and Adobe Illustrator together in
sign work for nearly 20 years. Both applications have their own strengths, weaknesses, bugs and handy unique features not found in their rival application. Being able to use the best features of both applications gives me more creative freedom.
It's also necessary for me to use both applications on a frequent basis since neither application is really all that friendly to files generated by the other. I get plenty of customer provided files made in either application. Some claim CorelDRAW can generate an Illustrator file good enough an Adobe user wouldn't tell the difference or vice versa. I beg to differ on that. Plenty of effects made by either application can be thrown off very badly when opened in the rival application. Some effects are application-dependent and cannot be exported. If I need an Illustrator version of a Corel generated piece of art, I must proof the art to see what "breaks" when it is opened in Illustrator. Same goes for moving Illustrator artwork into CorelDRAW.
I do a great deal of
sign design work within CorelDRAW due to its much larger art board. BTW, I haven't been able to make layouts of 150' work well (start getting "object not on surface" warnings). Layouts up to 100' X 100' in size are do-able. At that level you're prone to get the "This zoom has exceeded the boundaries of the drawing space" warning. Most
sign projects fit in the CorelDRAW art board at full size comfortably. The 227" X 227" limit in Adobe Illustrator (and InDesign) doesn't fit quite so much stuff. I end up working on things at 1/2 or 1/4 actual size, and make sure to have clear notes included in the layouts.
CorelDRAW is also very good for its object editing tool set. I can usually edit vector objects a lot faster in CorelDRAW than Illustrator. To get some of the same tools in Illustrator users are forced to buy plug-ins like CADtools. CorelDRAW has some unique effects not found in Illustrator, such as isometric 3D extrusion effects.
What I like about Illustrator: it is more precise with certain kinds of vector effects, like applying outline effects to shapes and open paths. The end results are often cleaner and more reliable than what CorelDRAW generates. Illustrator's color output for print is more reliable. Illustrator is vastly more integrated with Photoshop and other Adobe applications. I can paste Illustrator vector paths into Photoshop, Fireworks, After Effects, etc via AICB paths on the clipboard. Corel has never been able to do that.
I could go on and on with feature comparisons of what one app or the other has or lacks. Suffice it to say, I can't put up with running CorelDRAW exclusively or Illustrator exclusively. I won't do it.
I'll also say both have had their share of anger inspiring bugs and areas that need improvement. Illustrator still has a ways to go mend fences with angry former Freehand users (Adobe bought and then killed that rival vector app). It's annoying that every Illustrator release lately has been breaking third party plug-ins right and left. Corel has been goofing up things lately with CorelDRAW X6. I really HATE what they've done with type handling in the latest update (16.4.0.1280). Corel is throwing out half-baked updates just to introduce new features for "premium membership" subscribers. And they're cooking in new bugs while doing so.