Do you feel that Tactics Trainer, Chess Mentor, or Chess Videos provide the most useful practice to you right now at your current state of chess knowledge? Why?

I dont use any of them but if I had to pick it would be videos. Although I tend to watch them at chesslecture.com

Perhaps I should add (4) play vs computer, and (5) play vs people?

Tactics trainer is good for teaching you how to watch for situations to exploit. I also like playing against people to keep my creative juices flowing.  A live opponent will do completely unpredictable things. You have to be ready to "think on your feet".