Which object orientation is the best?

When printing / slicing objects, its always a good idea to see how much time & material the object will consume in the print. Less is better, however there will be parts and surfaces that will require a structural support (so that the object will not collapse)! But keep in mind, supports can take their toll on the overall print quality, so it might not be as smooth / appealing as without support.

Alternatively, you can even work around this by placing / printing majority of items by having them laying on their flat side.

You could even “cut” an object into parts, print the items in half and in the end attaching / gluing them together, having the result prints having substantial quality!