LSD or heroin?

My friends and I were talking about drugs the other day and I was wondering what the OOT's take is on this senario.

The situation is as follows: You have a choice between doing one hit of LSD of one dose of heroin (shooting up with a needle, not smoking). Based only on long term consequences which do you choose?

Heroin has seemingly no long term effects from a single dose, however LSD stays in you spinal fluid and brain forever. I picked heroin because the only downside is possible addiction (plus I've heard its supposed to kick ass). My friends told me that shooting up one time with heroin will get you hopelessly addicted. I shrugged this off as scare stories from the anti drug crowd.

What do you guys think? LSD or Heroin. Also is Heroin really that addictive?