The Optimus 7 without a doubt.
Windows Phone 7's OS is quick, snappy, and intuitive.
It is an overall great phone, whereas the BB is old and washed out.
Just my opinion.
Both phones have their up and downs its just reallly what you want in your phone, i say go play with each one at the store and see which one you like better
I understand, but this is what I do. Put your font size on like 6 or 7 (It's small) so if someone bbms you, you can read the message or part of the message depending on its size. If you don't want to talk to the person or answer then just simply delete the chat and it'll still look like you haven't read the message.