Thanks for the comments so far 
Theres many reasons to change, probably just as many to stay the same.
One of the issues, is consolidating outfront onto one server, currently its on a couple.
One server makes admin easier.
Although the NT server will run UBB, it tends to not be easy to modify (unless you want to muck around with cgi)
I prefer asp, so it means I can be more reponsive to providing features that people want. "Printer friendly" for example, being one of them.
To me, the use of avatars provides a "personalisation" (If thats a word
of users - more recognition.
Snitz offers extended profiles, so if people want, they can add more about themseves. Its always interesting to read about others, what they do and what they are up to, as part of a community.
Image loading? yes and no. Caching to a certain extent will remove problems, but most images are 2-3k and a topic will contain 10-15 posts max.
So as you can see, from the design, its the same but different. On average, I hope, a better different 