(Original post by Zorg)
Well the answer to that is easy. It all depends on if you are right handed or left handed.
OP the two phones are very different, you may have realised this but bear with me, the iPhone 4 is very much a media oriented phone; games, music, internet ect. The Blackberry Bold is more a business phone; huge battery life, great communication software (BBM).
Another contender you may not have considered is the HTC Desire (what I'm typing off of now, no bias
) very good phone, cheaper than the iPhone 4, very media oriented especially Facebook and Twitter. The only real con with the HTC Desire is the app market, it's not filled with as many gems in Apple's store but they're there and I'd say there are more than in the Blackberry App World.
The Blackberry would be a great phone if staying in contact with friends is your priority; BBM. Although having only 2 friends on BBM is rather pointless. Also if you type out loads on your phone (yours truly, sorry about that), make sure you know which you'd rather on-screen keyboard or a physical QWERTY keyboard.
The iPhone 4 is an amazing piece of kit, it has an amazing screen, great support and the Apple logo
It comes at a price though, namely your wallet.
If you do consider the HTC Desire, I recommend you buy an unlocked unbranded handset and put in a sin of your choice, this way you're set up to instantly get Froyo; Google's newest iteration of Android. Buying a handset from a network provider will mean you'll get froyo later in the next few weeks or so depending on the carrier (one of the cons of Android is fragmentation, Google it)
Sorry for the epically long post. I'm at work and I love showing off my inner geek
EDIT: Should also mention I own a HTC Desire, my sister own's a Blackberry Bold II 9700 and my housemate is an Apple fanatic.