Blender and Modo are both very good products while I think Modo has a more refined modeler, texture system, and animation approach. Modo is not geared like Blender to do everything, but what it does it does very good and often better.
But with the new Blender 2.5 there are many new add-ons coming to Blender which enhance modeling experience.
I think the differences are in the details as both apps share a large common tool set.
I am not sure why people are bashing Maya - because when it comes to offering diverse toolset for modeling it actually can do everything from polygon to sds to nurbs and nicely also convert between them. You can also customize Maya so it works for you with hotkeys like in Blender. Sure it is not a 20 MB software and it is not cheap.
Because you mention mechanical modeling and I am not sure what you budget or needs are but maybe this might be an option:
Maya has both polygon and NURBS in one system and can convert Subdivision surface into NURBS.
The same experience you can have with Rhino NURBS Blender SDS and T-Spline plug in for Rhino to convert polygon sds into NURBS patches.
If you have a lot of money you can get solidworks with the T-splines plugin and have polygon SDS to NURBS conversation on the fly inside a parametric design tree.