With both popular diets being low carb and high protein, Whole30 may seem the same at first glance. It gets even more confusing when you consider that all Whole30 recipes are Paleo friendly, but not all Paleo recipes are allowed on Whole30. Let's contrast the two and see where their differences lie.
The Whole30 Diet is a clean-eating program designed to reset your metabolism over a month. It's an elimination diet. No cheat days. No indulgences. No grains, dairy, sugar, legumes, or alcohol. The diet also doesn't allow for "diet-friendly" versions of foods not on the diet. No "Whole30 nachos" or "Whole30 Twinkies." It focuses on whole foods only.
Developing from the belief that our digestive systems have yet to evolve to handle the modern diet, the Paleo diet is named for our Paleolith ancestors and seeks to mimic their typical way of eating. It is less of a diet and more of a lifestyle. Like Whole30, it cuts grains, dairy, processed sugars, legumes, and alcohol, but isn't quite as strict. Since it's considered to be a long-term eating plan, many view the plan as more of a mindset or a template. They "cheat" once in a while and adapt the plan to fit their lives.
The duration of the eating style is one of the major differences between the two. Since Paleo is a lifestyle rather than a diet, it's easier to study the long-term effects of this way of eating. Paleo has been found to reduce blood sugar, blood pressure, and BMI, as well as raise levels of good cholesterol. There is also evidence that it may help control Irritable Bowel Disease. While there don't seem to be any studies done explicitly on Whole30, low-carb diets in general have been linked to weight-loss and lowered risk of heart disease.
Another difference is that Whole30 doesn't allow for any sugar, but Paleo only cuts out refined sugar. This means that on Paleo you could use natural sweeteners, such as honey or agave, but not on Whole30. A third difference is that Paleo doesn't care if you make diet friendly versions of "bad" foods, such as banana pancakes.
Many use Whole30 as a segue into Paleo or a reset if they get too far off track. It can be a good way to get used to the idea of cutting out processed foods before doing it long-term.