What a sh*tty choice for me. lol If I had to pick, I would go with piercings. Tattoos look really bad to me. It's a boner killer. I would be fine with maybe a nose stud, pierced belly button, and of course pierced ears but no gauges. I haven't looked into that many piercings so I couldn't what else would look good. No pierced nipples or vagina.
I love tattoos, piercings, tunnels, everything. But if I had to choose just one, I'd prefer tattoos. So hot. On a guy, I like tattoos everywhere. Except on the lower back and on the ankles (except if those are part of a bodysuit, in that case they are acceptable).