You know how in FullMetal Alchemist: Brotherhood, Ed and Winry are often at each others throats with the occasional slapstick in the form of the guy getting half-killed with a wrench, yet Winry still shows that he cares for Ed. I like to think of Ash and Iris having the same relationship, but are either too stupid to notice it or too scared to openly admit it yet.
Ash and Dawn have already given the impression that they are good friends from the beginning. The only times that you've seen them argue with one another was during the arbitrary "The Bicker, The Better" episode and when Ash does something really, really stupid.
If Ash and Dawn were to have a first date, I would easily imagine it being at a restaurant or a quiet picnic, but if it were a first date between Ash and Iris, the first thing that would come to mind is a playdate in a forest (ideally, the forest Iris played in when she was still living in the Village of Dragons) surrounded by dozens of Pokémon. With Negaishipping, you would be more likely to get action up the butt, and the conflicts would be moreso external; however, with Pearlshipping, the main thing would be internal conflicts (which we actually got some of in the canon material with Dawn in her slump and Ash feeling bad after his first 6 vs. 6 against Paul at Lake Valor). Don't get me wrong, I enjoy Pearlshipping, too, but internal conflicts are harder to pull off than external conflicts. If the character is too troubled by external conflicts, he just becomes another Ichigo Kurosaki or Tomoya Okazaki (a stagnant, samey character whose only defining traits are how much he cares for his friends and how much life has spat on him), but if he's not troubled enough, he seems like an arrogant ***hole.