I don't have a pearl but multiple friends do and it seems like a budget BB. A sub-par version of a platform already described as lackluster by past users probably won't stand up too well against an iPhone.
iPhone has a bigger screen, works on 3G, I'm also assuming it to have a better processor, more RAM, and better software that compliments the hardware. Plus it's prettier.
I had the original pearl and I just didn't like it. For just a phone it was ok but I couldn't get into the crunched keyboard and tiny screen. There are people who love these phones but if your going for a smart phone this would be the last choice to make. There are many other smartphones and blackberries that knock this one on its tuckus