The best opportunity is one where you can get an independent project in which you contribute something and have adequate supervision (either from the PI himself or surrogates such as graduate students and postdocs) that you can have a meaningful experience. You need to be able to go to interviews and describe what your contribution was, even if it didn't lead to publication, and your thoughts about the overall scope of the project. Publications are nice, but not critical, and it's better for you to be able to describe your work in the future and get a notion if PhD work is even for you.
I can't tell from what you're describing which of those experiences fits that. I'm a little confused, in fact. Is the PI leaving? If so, are your options
1) Stay in that lab and keep working on that project with the PI not around - vs -
2) choose a new lab
Or is it actually, PI is leaving:
1) choose new lab #1
2) choose new lab #2
If you're more specific, I can perhaps give you more advice.
I would stay away from a lab where you are going to be doing menial tasks for a number of different unrelated projects. Even if you get your name on a paper you will have a hard time understanding or explaining your contribution in a meaningful way. I would focus on trying to work on one project (or maximum two related projects) so that you can really get a good understanding of what you are doing and why you are doing it, such that you will be able to explain it effectively years down the road.
It's unlikely that you could be effective with a completely independent project at your stage, but you could get a well-encapsulated piece of someone else's project, or you could be a helper for someone else (like a grad student or postdoc) who has a focused project.