Well it depends on what you like to do most. Do you like to lane, or jungle?
Kalista
Pros
-infinite chasing passive
-can do a lot of damage
-can harass
-can be hard to gank
-good pretty much all game as long as your team isn't loosing horribly
Cons
-ult requires your teammates to be heavily coordinated
-any silence prevents her from using her passive
-ult can only be used on one teammate (Kalista gets a unique item that binds her, to her lane partner, which she can use the ult with)
Kindred
Pros
-good jungle sustain
-can gank frequently
-rarely any mana issues
-dragon solo at level 6 (if you have enough passive stacks)
-ranged slow on E as well as %max health damage on it
Cons
-not the best mobility
-jungle is pretty much the required role
-ult requires team coordination
-passive stacks are required to make anything meaningful happen as Kindred
So it's really what you prefer doing most, and which champion sounds more appealing to you.