rpart vs. randomForest

I think you are misunderstanding what randomForest does. It is not an
optimizer that spits the "best" tree back at you. It grows a forest of
trees (as many as you tell it to but 500 is the default). I would stick
to rpart if you are having trouble wrapping your head around
randomForest. Tree models are being used in many fields now and you
should be able to find an applied guide in you field with a little
effort.

Good luck, Andy