You can't generalize like that. I was 'generally happy' with my iPhone 3G, but I wanted a change and went to a BB 8900, and I've been very pleased with the switch.
The iPhone and BB each have their own strengths and weaknesses, and for some people, the BB may be a better choice. I love the way the BB can do true multitasking and backgrounding, which is very useful for me because I like running IM on my phone. And to top it off, I can do it on the BB without completely killing the battery.