I voted ink but then I read this.
Ink will last forever but you could forget an average vacation, those places though could be a pretty big deal. Go to Asia, get a small/affordable tattoo by a local artist in their style. Problem solved.
I hate getting ink on vacation cuz once its dont you are very limited in what you can do. Especially since I dont do small ink I go large with at least a min. of 3 hours under for a session. Im thinking of going towards ink since I already went to London this school year.