USING LARGER NO OF VIAS REDUCES THE RESISTANCE FOR SURE BUT BY USING MORE NO OF VIAS THE PARASITIC CAPACITANCE INCREASES WITH THE ADJACENT NETS.
SO DEPENDING ON UR IMPORTANCE U CAN CHOOSE ANYTHING.
U CAN TRY THESE BY EXTRACTING THE LAYOUT AND SEEING THE PARASITICS.
The reduced resistance is not parasitic... is the CONTACT resistance what is drastically reduced when you increase teh qty of VIAS... now, if the capacitance (parasitic) increases (thing I'm not that sure) and will affect you in some way let me say you WERE DEAD a long time before...
I think if one of the parasitic capacitance contributers is the vias effective (lateral or cross-section or..) area .So The vias distribution will have a role as well.