I actually done some testing and strong Bair is just as powerful as Nair. When I say just as powerful I mean they are the exact same. I set C. Falcon at a certain part on FD with 128% and performed strong Bair and then Nair. Neither killed, I bumped it up to 129% and both killed.
I done this to several other characters until I finally just accepted that strong Bair and Nair are the same. I prefer Bair over Nair because Bair is safer over the pit and Bair has more range.
IMO Nair is best as a f-tilt finisher when the foe will probably not get hit by both u-tilt hits or have a bunch of damage so u-tilt wont hit. Besides, everyone knows that at lowish percents f-tilt> reverse DSmash is the best.
You have a chance of doing 20% with it. Rarely happens though, but it is still a better idea than normal DSmash.
Also, if you feel like you probably aren't going to kill with USmash or if they can't get tilted for very long (floaty) end with USmash. USmash does like 30%!!!! That is the equivalent of most tilt locks and and 20% more than most every finish. I use this often against Peach and Kirby.
Oh, and as an added mix up.... f-tilt> jump over them> chain is an amazing mix up. If you keep it in your pocket and rarely use it you can get away with it often since most of the time they are expecting another f-tilt and are trying to air dodge.
Oh, and the reason why I have not made the tilt lock video yet is because I am replacing my old video Hyrule Rouge. My old video has a lot of stupid stuff in it and needs updated badly. So that is my current project.
Speaking of which.... what do you think I should put in there? Here is what I have lined up:
Proper recovery angles
auto snapping
DACUS
GR> DACUS
ground b reverse needles
chain lock
reverse chain lock
chain jacket (considering removal)
auto cancel aerials
f-tilt lock
f-tilt> USmash
all f-tilt finishers
jab cancel> grab, jab cancel> jab, jab cancel> DSmash> jab cancel> f-tilt and jab cancel> Nair
needle glide and vanish glide
uses of crouching (considering removal)
Alright, add or remove at will. Just give me a reason why you think the way you do.