Relative flexibility can matter a lot. For those of us with chondromalacia patellae knees, keeping our hamstrings loose is a key part of being able to ride without doing permanent damage. Now, what "loose" is varies a lot. I have to do a lot of stretching and push the limits of tearing stuff to occasionally be able to just barely touch a toe. The risk of injury is so high I simply don't. If I can get withing a few inches, I'm happy and so are my knees. My sis, on the other hand, used to be able to put her palms down flat on the floor.

Edit: Stems - I like them long and low. My body is like a leaf. Lightweight, long and with lots of wind resistance. The lower profile I can keep the easier going fast or upwind is. I also have arms that go on forever (and well past most of my shirtsleeves).