One of the things that a Blackberry does better than an iPhone (or any other phone) is email.
That said - yes you can sync the iPhone with Outlook and the soon to be released iPhone OS4 will add improvements to the current system.
One of the biggest strengths of the iPhone is it Internet access and screen size. I have an iPhone and it is one of the best bits of kit I have ever had.
I do not know if you saw the news item this week. Standard Charter bank, after pressure from staff are now offering the iPhone as an alternative to the Blackberry for their staff. It is said that many other companies will now follow suit since Apple have improved the security on an iPhone to the standard required by business.
The best way is to go into one of the mobile shops that has both iPhone and Blackberry, get them in your hand and see which one does it for you.