Hi,
Architect here. In most situations, sistering should be cleaper than replacing the joists. Again, LOTS of variables to consider, mainly the conditions of the masonry pockets (how the existing joists intersect the wall) and the conditions of the underfloor. Contact a GC and ask those questions... those two variables should drive the decision if sister or replacement.
I hope this helps!
ileana schinder
PS: feel free to reach out if it doesnt
ile@ileanaschinder.com