My Testimony: Madun
I thought this was a good place to start and do my part.
I haven't shipped anyone else but I wasn't there from the beginning either. As a small child, I loved Pokémon but lost interest and stopped watching sometime before AG. Misty was getting on my nerves and I couldn't really picture her together with Ash. I didn't know about shipping in general until much later. The concept seemed a bit weird to me at that time and I couldn't imagine myself being a part and it seemed unlikely that Dawn was going to be a part of this since I missed DP entirely. As you can see, I was wrong, it didn't matter whether it was old or new. I don't even know why, it's just a kind of fun I'd been missing for a long time.
It wasn't a single event but more of a slow process. It started with discovering High Touch, which sparked my interest and from there, I gathered more and more information. There was something different, refreshing about them (I'll come to that later). Personally, I can't understand how anyone can possibly support a shipping without knowing anything about one of the people involved so I got to know more about them until I was sure that they simply belonged together. Watching DP only confirmed this and to be sure, I also had a look at other shippings but I couldn't find anything that could compare.
It was High Touch, whose lyrics didn't seem like something I would say to someone I consider a mere friend, let alone sing it. No, there was something more. Besides, they obviously had a great chemistry, something Ash and Misty were lacking in my opinion. And not to forget, they looked great together even though it was only one picture. As I said, it didn't turn me into a Pearlshipper in an instant but the impression was positive enough to set a process in motion that resulted in me ending up as one.
There are a lot of things but the most important one is that they're equals in every possible way. I despise character who are simply there for someone else but those two are clearly not like that, although they can clearly draw strength from each other's presence. Although Dawn was far less experienced, she still managed to help Ash out in his journey. Hell, he even might not have made it without her as his rivals were so strong in DP. And in turn, he helped her overcome her own problems and allowed for a quick rise to the top (well, almost). This aspect on its own makes Pearlshipping superior in my eyes.
Another aspect is that their friendship is based on support and not, unlikely seemingly many couples nowadays, on conflict. They go out of their way to help each other out, putting the other's interest above their own. Of course, there are still arguments and that's a good thing since it would be unrealistc otherwise, but it's not nearly as bad as with others and they always quickly reconcile. That's possible they have so much in common, the same passions and the same determination to reach their goal, which they both had right from the start. There are far more similarities but these are the ones I consider most important as they allow them to achieve their goals together. Similarities are far more important than differences, the 'opposites attract' myth is highly overrated.
It's easy to make shippy moments in extreme situations but this couple also works in everyday life and that's important as their life will mostly consist that. In my opinion, it's more important than all the hints put together (although they do have pletny) since without a working everyday life together, they would quickly get annoyed. It's probably as harmonious as it can get and their similarities allow it. Those three main points are entwined and boost each other and that's what makes it so strong.
There are also other points but it would take far too long, those are the ones that got me the most.
That's hard to say because there wasn't a single moment when I became a Pearlshipper. I believe it was sometime around 2011 that I truly took an interest but I can't pinpoint the exact moment/day/month.
Just because something is new, popular, heavily advertised, it isn't necessarily better for you. On the other hand try not to let nostalgia cloud your mind, which is difficult at times as I'm not always successful in that regard. Pearlshipping is something that has grown to be something beautiful over a long time and still has it followers, despite the age, without the need for manipulation by the dub. I realize different people look for different qualities in couples but you should give it a chance before doing something like going for the current bandwagon-shipping.