Picatinny specs:
Slot width - 0.206"
Slot Centers - 0.394"
Slot Depth - 0.118"

Weaver spec:
Slot width - 0.180
Slot centers - Varies with mfgr.


So CAN you interchange? Certainly possible, but it depends upon your specific equipments tollerances.
Like has been said, neither is "Better", simply different.