How do you pick a passionfruit?

Until we visited Australia, I was convinced I hated passionfruit. Of course, while we were there, I had plenty of opportunities to discover that I was completely wrong... and, apparently, the thing I actually don't like is guava (the two fruits seem to get paired a LOT in the US, so I guess it makes sense that I didn't know which flavor was which).

Anyway, passionfruit is finally starting to show up in local grocery stores this year and I've realized that I have no clue how one goes about picking a good passionfruit! Should it be wrinkly? Should it be firm? I've been going with the standard fruit picking philosophy that it should be heavy for its size... and the ones I've picked so far have been okay, but I think it's been more a matter of luck than of skill.

So, any suggestions?

And, btw, fresh squeezed passionfruit pulp over homemade cheesecake? Probably one of the best combinations EVER!