It also depends on how you will be using the iPod Touch.
Is this something you will be using throughout most of the day? Do you need the functionality of a Blackberry or do you really only use it for text messaging? I think we would need a little more information to really help you with it.
For me personally, I only use an iPod when I am driving, which is maybe between 1 and 3 hours a day. In this case, I have a curve (8310), and an old iPod nano that I will upgrade to a touch when it kicks the bucket. It will work fine for me because of my needs for an iPod, which are minimal. The increased functionality of an iPod Touch will be nice for when I travel, but for a typical day, I don't use it very much. It really depends on your situation which would be the best way for you to go.