Transitions of any kind increase the need for bandwidth just like fast motion or complex backgrounds. It is always a compromise. That is why in preparing for the web I tend to crop in on all of the shots. I also produce a second edit of the piece just for the web with less dependeance on trasitions and more static shots. Remember that a moving camera is worse than a moving subject. There is no pat answer to your question. My answer is, when I want the best for the web, I produce the piece specifically for the web and I work with the limitations.

K