Judging from the two videos, both models are water / splash resistant.
The Susan model has a scrollwheel as a navigation option, 5 megapixel camera and some type of camera light. It seems to be a camera on the front end which indicates video call posibillities.
Sony Ericsson Sunny is a slider model with a 5 megapixel camera and flash
Sunny
Susan
These two findings any much more was found in the Esato forum thread SE-09-Portfolio