I assume that both Première and Encore do not work so well (in terms of speed / performance) with MPEG files and prefer uncompressed AVI.
That all depends on the computer its running on.
What is the purpose of this question.
I assume you mean that MPG files take more processor but less disk and uncompressed AVI is the opposite
The purpose is to establish a general principal.
Towards what end? There are quite a few variables here.