I don't see why one would pick Sha over Strix. Let's compare them:
Health: 2000 vs 2100
Damage: Sha only deals a 1000 per shot vs Strix 1200 per shot. Sha's fire rate is one shot every 1.5 seconds (with Recurve one shot every 1.275 seconds), while Strix can technically shoot every second, but you have to scope after every shot so it takes a bit longer, so it's approximately the same fire rate while Strix has more damage per shot. Sha's weapon is a projectile which can't headshot (and has travel time, so it's harder to hit), while Strix' weapon is hitscan and can headshot.
Stealth: Sha's stealth abilities are predictable (he always jumps back when he uses withdraw, so you can track him, especially if you have some blast damage), and Withdraw only lasts 2 seconds. His ult has a loud sound cue, so you can hear where he is and track him, especially with blast damage. Strix is way more flexible with his stealth, he can enter it when he wants, he can restore his stealth energy, he can get movement speed in stealth, and he can decide when he goes out of it.
Close range: Strix can pretty much burst down any flanker easily, and his ultimate can also win him the 1v1 if he messes up. Of course Sha has his Stun + Planted combo but Planted has a long cooldown, he is stationary so it's easy to burst him down (if other enemies are around), and it only stuns if they hit a wall, so the stun isn't guaranteed.
The only small advantages that Sha has is that he doesn't have to reload and that he can move around the map faster (with Wanderlust and Poise and if he picks up Nimble he is really fast). but I don't think this can compensate all the other disadvantages
I don't wanna say Sha is bad, but I feel like there is literally no reason to pick him over Strix.