I'd go with Soundhax. And if Nintendo patches Soundhax then don't update and try to get Freakyhax.

Freakyhax most likely won't be patched.

 

ninjahax is awesome when I was waiting for a9lh back on 11.1, it can't be patched and it its working on the latest update... just get cubic ninja used from gamestop.com for $20 and relish in the userland hacks while you wait for the E.O.L. jailbreak... with the switch out, the 3ds life line is going to end eventually.. I predict it to end in 2018... because the releases are getting smaller and smaller until the game production is shoved into the switch...

 

of course ninjhax can be patched, it was totally broken on 11.1/2 I can't remember right now, but smea fixed in in a twitch live stream

 

Definitely Soundhax. After all this time Ninjhax still works, they can put out a new patch for Freakyforms that patches the exploit but there's nothing stopping you from not installing the update, or deleting it if you have it already, since the exploit can be done completely offline AFAIK.
I have a copy of Cubic Ninja that I may very well never need again but I'm still holding onto it, it serves as a reminder of the origins of 3DS homebrew and is just a cool thing to have