Silo is great, it's intuitive, versatile and quick... BUT... they've stopped updating it. I think they've moved on to more profitable things.
So? It's propably the cheapest modelling tool that's so powerful. And it works - no matter they work on it further or not.
As for Blender - yes , it is free and has lots of features. But note that as many other software on the market it is not aimed at model makers - rather cgi art , gameart, animation. So there's a ton of confusing tools for us, tools that in fact we don't need. I would not recommend it to a beginner. Also I have to admit it haven't "clicked" for me. Somehow I felt I'm running around things when I tried modelling within it.
At the same time a friend of mine likes it quite much, while despising a tool I found really nice and intuitive (Modo). So I think it depends - you'll have to propably try for yourself