For fresh cut French fries I have noticed this season that there isn't much difference in the price of an 80 or 90 count No. 1 potato versus a No. 2. Are there other advantages to using a No. 1 potato for my fries?
Given similar pricing, which really varies from one crop to another, it may be very advantageous to use No. 1 potatoes for your fries. No.1 potatoes have less defects and are more even shaped in general, so are easier for the kitchen to get use out of the whole potato. Yields could be better. If you put the bags or cartons out on display, like some hamburger fast food or fast casual operations, the No.1s may hold up better and not break down as fast at room temperatures, as they probably have less cuts and bruises.
The carton count size is usually a tighter range than is allowable in a No. 2 carton or bag (yes, you can get No. 2 potatoes in cartons, ask your distributor or produce house) and so the potatoes will be of similar size. For an end use of French fries, if the potatoes are of uniform cross sectional area and size, as a general rule they will cook at the same rate. On the other hand, if they are not uniform size, then the smaller pieces will be more thoroughly cooked, and perhaps overcooked, long before the larger pieces are finished cooking. Also, don't overfill the baskets before placing the potatoes into the fryer. When blanching or finish frying, if the cut potato strips are stuck together, this will influence how evenly cooked the fries will turn out.