When making comparative claims, how close does a substitute have to be to the product it is referencing?

When making comparative claims, how close does a substitute have to be to the product it is referencing? 

Would it matter if I was comparing my Reduced Salt Original Potato Chips to the leading brand of Original Potato Chips or my own brand's? Would I have to note who I was comparing to on my label? (20% less salt than the leading brand! or 20% less salt than our original flavor!)

How about if I was comparing my Reduced Salt Spicy Potato Chips to my own brand's Regular Potato Chips? In this case, is flavoring important to the identity of the comparison? Would I have to compare to another brand's Spicy Potato Chip?

From 21CFR101.13

(d) A "substitute" food is one that may be used interchangeably with another food that it resembles, i.e., that it is organoleptically, physically, and functionally (including shelf life) similar to, and that it is not nutritionally inferior to unless it is labeled as an "imitation."

Where I get confused is the use of "organoleptically... similar to." because I have seen vegetarian burgers compared to beef burgers as "reduced fat" options but since organoleptics implies taste, the similarity between the burgers seems arbitrary. In the burger case, is it because they would use language like "Vegetarian burgers contains 30% less fat than 80/20 beef burgers" ? Would that format be applicable to the potato chips example? 

Thank you for any insight/thoughts about this. 

I think this link might help you out a lot:  https://www.fda.gov/.../81606/download

N28. What is meant by "product category" when the regulation say that for "less," "fewer" and "more" claims, the reference food may be a dissimilar food within a product category that can generally be substituted for one another in the diet. Are these product category the same as the 139 product categories used to describe theRACCs for serving sizes?

Answer: These are not the same as the product categories established for serving sizes. The agency intentionally did not define "product category" in the final rule in order to allow for the use of a flexible standard. It intended that comparisons be made for foods that are interchangeable in the diet, recognizing that sometimes these foods would be dissimilar, for example "apples have less fat than potato chips").

N29. When would such a claim as described in section 8 N28 (above) be considered misleading?

Answer: A claim would be misleading if it compared two foods that are not reasonably likely to be used as alternative food choices for a specified eating occasion, for example, "apples have less fat than sour cream."

Considering both of those questions, I think you mainly have to be accurate with how you make your claim.  I've seen some compare themselves to "a leading competitor" or "leading national brand", and I've see companies make the comparison to their own flagship product.  In the case of spicy chip vs regular chip, it should be compared against a like product (to account for similar levels of spices and sodium).

But I'd glance at the whole guidance document still, as there are some interesting facts outlined in making "light" claims that also get into comparing to a market leading brand that could carry over:

N38. Is a market leader always an appropriate reference food?

Answer: No. For example, if there are two market leaders with widely different nutrient profiles, selecting the one with the slightly higher market share for the reference food could be misleading. In that case the nutrient values for the two market leaders should be averaged together to determine a nutrient value for the basis of the “light” claim.

The reference posted by jfrey123 is great.

Here's something I found on page 91 about relative claims.

“More” and “Less” (or “Fewer”)

(1) An established regular product or average representative product, and

(2) A dissimilar food in the same product category which may be generally substituted for the labeled food (e.g., potato chips for pretzels) or a similar food.

Based on this excerpt, you can absolutely compare 2 types of potato chips.

You could even compare your potato chips to pretzels.

There are a few caveats, so as Jfrey recommended, check out the document yourself.

Just make sure your numbers are accurate and document these comparisons in your records.

I would write a quick report with pictures of the Nutrition Data on both products.

This will allow you to prove your claim if an authority ever comes asking.