the speed is dependent on so many factors,
build time for "prefabs" has not much to do with it.
(unless you have a scene with hundreds of thousands of
polygons).... in matter of fact, once you lightmap
them, it is quicker than dynamic lights..

I personally don't like using the WED to make the models,
and I am able to convert models I made through Wings 3d
into "geometry" so I can use radiosity lightmapping,
but became discouraged with how long it takes to get the models
in and light them.

I just make my models in Wings + Fragmotion, then load it
(so it is light-speed fast to get my models in),
and build light-speed fast.... and I use shaders and
dynamic lights...

It is a shame, because I would really like to use radiosity,
but it takes too long to load my levels (and build)....
maybe I am doing something wrong?