It could also be harder. Say that 10 bits of current 16 bit parameters are useful; then to match the capacity you would need 6 ternary parameters, which would potentially be hard to find or interact in unpredictable ways.
Perhaps if you needed a larger number of ternary weights, but the paper claims to achieve the same performance with ternary weights as one gets with 16-bit weights using the same parameter count.
It could also be harder. Say that 10 bits of current 16 bit parameters are useful; then to match the capacity you would need 6 ternary parameters, which would potentially be hard to find or interact in unpredictable ways.
Perhaps if you needed a larger number of ternary weights, but the paper claims to achieve the same performance with ternary weights as one gets with 16-bit weights using the same parameter count.