I can't "compare" because I have never had a Blackerry.
However, my family has Iphones. Hubby and daughter have the Iphone 3G (newest model) and love them. I have the Iphone that came out first and I love it.
I will say that their phones are faster. We got daughters with the largest amount of storage because she has a ton of songs, games, apps.
We will probably never go without Iphones again. My daughter is on my package and our bill is about $170/month. We pay the fees for internet and then I pay an extra $30/ month for unlimited texting and pics. WORTH it.
Hubby has his own set up with a lot more minutes and he pays about $170/month for his.
I love it because I no longer have to take my laptop when we travel. I have my internet access.
Con: cannot put it on the warranty system with ATT, however, you can purchase an extended warranty (which we did with daughter).
Con: you can't text pics, you have to email (unless I have not figured something out)
Con: you can't automatically save text messages. (There is a way around this but time consuming...can be done) I'm talking about saving/sending to an email account vs saving on the phone.
IPhone is super light and easy to have in pocket. DONT drop it.
My vote is IPhone, we will not carry anything else.
Good luck