If length is also desired my experience leans towards first going for the stretch. Using heat and a routine that allows the penis to rest between exercises.
However, personally I love pumping, pumping provides immediate expansion that can become addictive. I have also found that the expansion last longer as you become more acclimated/conditioned to pumping, lol, this is good and bad. This is just my experience.
I still pump due to the satisfaction provided from immediate significant changes in volume; however, if you are looking for length I think heat and stretching routines might be your best bet.
It is easy to over-train once you become addicted to pumping and yes I personally feel that it can negatively impact length routines. This is not to say that some length cannot be gained from pumping, but I personally tend to feel that elongation exercises before girth exercises is most efficient.
Others with more experience might have alternate suggestions and ideas to best practice. I will say that when looking for length and also pumping, much attention to balance is necessary to achieve best results. I personally probably pump too much.
Others will provide additional support relative to suggested best practice.
