I guess it all depends on how your hair behaves. Try both and see for yourself. I know for me, it doesn't necessarily give me more definition when I wash my hair upside down, but it tends to give me more volume (which I love). If you do want more definition, try twisting and scrunching your curls when applying product, and blow dry your hair upside down.
Better to wash hair upside down or standing up?
What gives better curl definition?
I find that washing and styling with your head up gives more definition, whereas doing it upside down gives more volume. More volume does tend to give less definition though. Personally, I wash and style right side up, and then flip my head over and continue scrunching in product.