Would anyone here consider form•Z as an option if you needed to change software ?
Depends a LOT on your needs. If you can clarify your answer there a bit, I might be able to answer better.
formZ doesn't include RenderZone plugin by default, RZ's a added-cost option, and rendering output in native formZ is extremely limited without that, Vray or Maxwell, plugins. In terms of modeling, it's obviously more focused around CSG/NURBS work, but has a decent set of poly & sub-d tools as well, so potentially good in that regard. Never really played with animation in formZ, so can't comment there at all.
Also depends whether you're talking current formZ (v9) or an earlier version, and which edition.