The best way I can explain IHOP to anyone who is familiar with dine-in restaurants like Denny’s is this: IHOP is to Denny’s like In-N-Out is to McDonalds.
Comparing IHOP and Denny’s side by side… they’re pretty much the same place. They have similar menus, both are typically open 24 hours, and you’ll pay pretty much $7 for a burger at one or the other. That being said, I always viewed the food and service at IHOP to be a step up above Denny’s on average. The menu prices are probably a little bit higher on average, but not by much.
If you’re looking for an all night diner and what prompt service at the cost of an extra buck or two, IHOP is your place. If not, Denny’s is down the street.