There’s question one would ask for a job like this.
Are you or the webmaster going to do the compression?
W Who is the webpage’s target audience (alluded to in another post)?
Will it be video/graphics pros?
Corporate
Selling a product or service (and what might be the base income bracket of the desired customer)?
News
Is the video simply “talking head” or is there significant visual detail?
I find Quicktime is good for media savvy or artist/musicians
Window media Video for Corporate or Product/Service marketing (since they may not allow or want Quicktime Player on their systems)
Broadband data rates for people with some money to spend
Dial up data rates if it’s very basic news to reach people who don’t spend for broadband connections.
Data rate may depend on target region(s). Higher broadband data rates for urban areas. Lower broadband for more rural areas where they may be on very slow DSL or Satellite broadband (and even dial up).
With Quicktime
H.264 is good for advanced artists or tech savvy (since they need QT 7 and must know to update) and will give you best quality
Sorenson Pro or MPEG4 for those with older versions of Quicktime.
Flash is an option but the webmaster needs to know how to integrate.
Sometimes one may offer two (or more) versions for broadest reach.
The above are not rules. Just guidelines and only my personal ones at that.