So it seems all of these can work the same:

RS2Object tree1 = objects.closest("Oak");
Entity tree2 = objects.closest("Oak");
NPC tree3 = npcs.closest("Oak");

What are the differences if they all accomplish the same job of finding the closest oak tree? [What is the right tool for the job?]

 

Continuing on it looks like they all can be interactable:

tree.interact("Chop Down");
tree2.interact("Chop Down");
tree3.interact("Chop Down");

Again what is the right tool for the job if they all do the same thing?

http://osbot.org/forum/topic/93981-guidetypes-of-entities-and-how-to-use-them-correctly/

http://osbot.org/forum/topic/93981-guidetypes-of-entities-and-how-to-use-them-correctly/

 

Well that was easy, thanks.

Entity is the super class, meaning that RS2Object and NPC both extend it. Don't use the super class unless you know what you're doing; the OSBot API makes a lot of convenient decisions based on the child type (especially in interactions).