Most things a baryonyx can do a sarco can do just as effectively or better here is a list of what they are good for.

Baryonyx:

Pros: fast on land, can fit in almost every cave, has a bigger attack aoe, can stun things in water, can be bola'd and takes less tranqs to tame, can build up speed by spam jumping

Cons: slow in water, slightly weaker, can't stun big dinos (mosa, ect), usually needs a pen to tame, only eats fish, saddle unlocked at a higher level, saddle requires a smithy to craft

Sarcosuchus:

Pros: Fast in water, best turning radius in the game, instantly regains stamina underwater, stronger than bary, lower level saddle, can be "ridden" without the saddle, slow speed when wild makes it easy to tame

Cons: slow on land, small attack aoe, deathroll is kind of useless, can accidentally knock itself out by lunging/deathrolling, takes longer to tame, there is a glitch where occasionally sarcos will die or almost die when they exit water, has a hard time hitting bugs