SE30 - gives you a run time analysis and points out the issues more at design time.
ST05 - Is the most useful if you want to track time taken for execution of each of the sections.
SM50 - Will give you a work process overview, not sure at a program level how can it help you.
Some times you will have to use a combination of SE30 and ST05.
I would like to use St05 personally.
if hlped mark points