"A" is my strong preference, for sure. "B" would require being more tightly bound up in my underwear than I would prefer.
Before puberty, I much preferred "B", as it was a lot more comfortable for me. "A" caused my exposed, sensitive little glans to be constantly thrust out into my underwear, where it rubbed annoyingly all the time. Once my penis grew to adult size and became able to hang downward, rather than stick straight out, that problem went away for good.
