Well its yes and no, depends on who you ask really.
Goodnites to me are pratically diapers just in a different style compared to the traditional tab diapers out there. When it comes to feel it generally feels the same as most diapers that are meant for that specific age group of said product and function as such. The main focus of it however is to make it look like underwear[though it fails] and just hold in urine.
While for the majority of the community Goodnites are a tight fit the small minority here who fit would probably tell you the absorbency of Goodnites is meh at best getting beaten by tab diapers. As for messing I would not recommend it really since they are a bit more tight compared to other products and etc meaning there isn't much space for that act to begin with.
Personally I think there's a definite distinction between pull-ups and diapers. If you say diapers, people are assuming you mean the tabbed kind that can be used for both urine and feces. Pull-ups more specifically refer to the kind that slip on like underwear and are geared towards holding urine. This means they don't really act the same way. They have different designs for different purposes, and it makes it easier to communicate what you are talking about if you use the distinction correctly.
There's also a distinction between products intended for toilet training and products intended for bedwetting; pull-up originated with the toilet training products but came to be used generically like "kleenex."
This thread should be moved to Diaper Talk, however.