well, i think this has to do with the effects you get from the various compounds. there are obviously a lot of things that androgens do (and some do more, or less), but the processes might not be very fast.
for instance, testosterone increases red blood cell production, thereby increasing endurance and the "pump." however, this is not immediate... testosterone signals the kidneys to increase EPO production, which signals the bone marrow to increase RBC production.
^does this answer your question at all?