I started using Sonia in MK11 and it has been a lot of fun.
Jax is still cool and all but I think Sonia is going to be my new main because her projectile loads faster.
The only issue with Sonia is that I hardly get her Krushing Blows or at least need to practice it.
Sonia also doesn't have many juggle combos but she makes up for it by being really fast and nimble on the ground. Check out this video of me playing with Sonia literally minutes after learning how to use her.