This topic always produces a lively discussion.
The truth is that there are several places where you can draw the line depending on the variables you're looking at. Some guys look at cc's, some at metal vs. plastic crankcase, some at porting. Some manufacturers try to draw the line themselves, some put a "pro" decal on a saw that's obviously not.
Husky has tried to solve this by coming up with a third category to cover those saws that are in the gray area between consumer and pro. They call it "landowner", and to me it just further adds to the confusion. But there are certainly saws in the middle of anyones lineup that aren't as good as the top models, but are obviously better than much of the stuff below them.
IMO, it's fruitless to try to identify where a line should be drawn to divide the pro from homeowner saws. I think you should look at it like a ladder, with the saws getting progressively better with each rung as you go up.