Is it reasonable to tell patients that Evenity lowers fracture risk by about 70%, while Prolia reduces it by around 50%?  

It depends on the skeletal site. A 3-year fracture relative risk reduction study of Prolia versus placebo revealed a 68% reduction in new vertebral fractures, a 40% reduction in hip fractures, and a 20% reduction in nonvertebral fractures. (Cummings et al., PMID 19671655) The relative risk of new ve...