Rhino: so-so; Grasshopper - Phenomenal!
It's all about grasshopper, kangaroo, and galapagos.
As someone used to parametric modelling in Inventor, rhino feels like a significant step backwards. Sure it's got way more useful surface and spline modelling tools, but it just feels klunky and limited. For instance, fillets need to be done in a specific order (large to small) in order to not break your model! Once a small fillet is applied, you'd need to revert to a save prior to the small fillet in order to apply a larger fillet to a touching edge. Lunacy :-(
However, if you model (or import) geometry, and apply interesting things in Grasshopper, there is significant power. Grasshopper has blown my mind. It's not perfect, but it's incredibly powerful, and fairly fast to use. I wish there was better documentation on all the various functions. Perhaps one day soon there will be.
Buy rhino only to get access to grasshopper and it's plugins.