hi,
there are lot of rosin compounds out there, each of them has specific use cases. each case need to be studied, we tested several solutions for laser manufacturing for example (it had to be moisture proof, sealed for avoiding power modification for the laser diode etc etc).
so for some apps you need specific rosin compound, for others it may be different (for example, if the board is heating a lot you may choose other rosin)
fluidity is also an important parameter in pcb compounds
regards, pierre