Professional film is made to the proper color balance right out of the factory. Consumer film is deliberately made with the wrong color balance, because it is expected to sit around in room temperature and/or in a camera for some time and "age" into the proper color balance. This is why you often hear the unexplained "rule" that professional films must be refrigerated, while consumer films need not be. Pro films are already where they should be in terms of color balance, so refrigeration slows any changes. Consumer film actually "needs" to age to hit its optimum color balance.
This being said, perfect color balance is not really critical. As long as it is not way off, it can easily be neutralized in printing. What is important is consistent color balance roll to roll (or sheet to sheet) within the same assignment or portfolio/project. As long as you buy films, pro or consumer, with matching emulsion numbers and that have been stored together, the color balance will match roll to roll or box to box of sheet film. However, professional films are easy to buy with matching emulsion numbers, because they come to pro shops in matching batches, and are often sold to customers in large quantities (often by the box as opposed to by the roll). Consumer films can be bought in emulsion-matching batches, though this is usually easiest at a pro photography shop, as opposed to at Thrifty or Price Club or the supermarket. Obviously, perfect color balance roll to roll was really only a huge concern for shooting transparencies for direct viewing by clients. Color negatives are easily corrected during the printing process that must occur for them to be viewed as positives.
When it comes down to actual emulsion characteristics, there is a lot of generalization that is made. Most professional films are made with "superior" technical qualities for "serious" photographers. They are generally finer in grain and more natural in color. They often push and pull better, and they come in more formats. However, aside from the format availability, this is not really what makes them "professional" films. It is kind of a chicken and egg situation. They are not pro films because they meet certain technical criteria; they meet certain technical criteria because they were designed solely to be shot by "serious" photographers.
The greatest differences are what I named above, and consumer films are generally excellent in quality. The Superia line (which has largely been decimated, sadly) is very high quality film capable of providing "professional-quality" results. In fact, there is (or was, till recently) a professional version of the Superia films. It's the same emulsion as the consumer Superia films, with the same characteristics. The differences are what I named above: proper color balance right out of the box, and availability in large emulsion-matching batches. These Superia Press packs were bought and shot by the truckload by newspapers and magazines, so they probably got more professional use than any of the current "professional" color negative films, even though apart from a slight difference in color balance, the emulsion is exactly the same as the consumer Superia.
In short, it is not really the quality of the emulsion itself that makes it "professional." It is the little changes made to allow for differences in how, and by whom, the emulsion is intended to be used.
