Since this is a broad question, let's split this up: Favourite to look at (on other people and such), and favourite to wear on yourself!

My favourite lengths to look at on others are probably waist, tailbone, thigh, knee, and ankle.

My favourite lengths that I've worn thus far have been mid-neck (which bounces up to about chin length thanks to my waves), APL, and Waist. I think I'd really like TBL but I've never been that long before. Anything past TBL would be too long for me, personally.

A lot of people seem to hate APL, but I'm really liking it! It feels long to me, but it's easy to wear down and doesn't really get in the way. My waves really show at this length, as my hair is long enough to be wavy rather than flippy, but not so long as to weigh them down. Before APL I was so impatient to move forward, but I feel quite comfortable here. I can also braid my hair, which is a huge plus!!

Enough from me, let's hear from you!