I usually always vend from Ocean's Depth, but I was wondering if there was a more profitable machine to vend from. What do you guys think?

It depends on what your going for actually :)

During the reading drive it would be profitable to vend at Blue Sky, since the book prizes are going to inflate... a lot. When new clothes come out, OD is a good one etc. xD

I enjoy expanding my wardrobe, so I spend most of my time at OD. But, I also go to blue sky in hopes of some rare books (or sometimes minions).

All clothings items are availiable through the OD :)

I unfortunately haven't completed the underwater map D:

I've never had any luck vending. You're better off selling the wizard tokens.

I like the Blue Moon machine seems to give out lots of things.