No difference - Hampton Inns all offer the same buffet-style breakfast at their hotels. There might be a difference in these terms when considering other hotels, but the Hampton Inn breakfast is standard across their hotels and there are no table-service restaurant breakfast options at them.
Probably no difference. Here's what you can get: "Waffles, oatmeal, cereal, omelet type eggs, bacon or sausage, bagels, yogurt, fruit, boiled eggs, pastries, coffee, tea, juice. over a year ago." [Trip Adviser]