I can't really live without having BOTH CorelDRAW and Illustrator installed on my computer. The two applications each have some extremely valuable functions unique to them the other lacks completely.
A few of Corel's unique strengths:
Better path editing tools, particularly at the control point level. It has taken to version CS3 for Illustrator to finally get some decent anchor point selection and alignment functions added.
Better variety of extrude effects. IllustratorCS2 cannot do parallel extrusion effects, which is mandatory for many of my channel letter drawings and for some other 3D sign cabinet technical drawings as well. Illustrator only extrudes into vanishing point perspective.
Corel has LOTS MORE in the way of fonts and clip art.
Corel has an easier to customize interface.
100' X 100' maximum work space size (Illustrator doesn't go above 227" X 227").
A few of Illustrator's unique strengths:
Better quality on path offset effects, stroke effects and a number of other operations that show off Illustrator's better floating point performance. Objects can be numerically dimensioned out to four decimal places (Corel only goes to three).
Tight integration with Photoshop. You can paste Illustrator paths directly into Photoshop as pixels, vector paths or vector shape layers. Corel cannot do that at all since it does not support AICB Postscript format on the clipboard. Freehand also supported it. Corel never did.
Superior type and color control. Illustrator also melds well with Adobe InDesign, which is even better on type control. Illustrator supports all the features of OpenType while CorelX3 does not. CorelX3 added Asian type support, but comes up short compared to Illustrator's implementation of it.
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Anyway, I hope some get the point that being a "fanboy" for only one single drawing application really doesn't make any logical sense at all. You're just limiting yourself. I might as well punch myself in the crotch as do something like that.
I've tried lots of different drawing programs. At the bare minimum I currently refuse to have any less than 2 of the major drawing applications on my computer. For awhile I had four installed (Corel, Illustrator, Freehand and Canvas) and have even had more than that at times. And that's not counting sign-specific applications and font editors either. I couldn't care less about brand names or brand worship. The only thing which matters is having enough creative capability in vector tool function. My artwork is what counts, not being "loyal" to just one application.
Maybe over time Illustrator and Corel will improve enough where having only one or the other will be enough. Right now that situation just doesn't exist.