INDEED Knowing what kind of work you do would help to give you suggestions.

But in general when you start using MoI you get the filling that, that is how Rhino should be...is all those little details that make MoI very attractive...MoI & Rhino are very similar products...and you could say Rhino is more advance BUT MoI is gonna get there in time, no doubt about that.

Also note both MoI & Rhino have similar limitations so my recommendation would be go for MoI & SpaceClaim Style or MoI & Inventor LT... (both for about $1200) Although Ill personally like to support SpaceClaim I choose Inventor and the main reasons are, a) DWG support is not working as advertised. b) they charge a ridiculous amount of money for the file format translators (inventor LT includes 3dm, Alias, DWG, Catia, ProE, UGS NX, SolidWorks, Sat, Parasolid, etc).