More and more users are switching to Blender not because of pricing, but because of what other users are accomplishing with it. In studios it's become quite normal to see Maya and Max users adopt Blender in their workflow. The community is thriving, and this is very attractive to new users as well. The attractive pricing (free) only serves to help adoption, but I think it also has to do with the simple licensing: Blender doesn't even need to be installed to run. Compare with the C4D trial: in a move to make it even more hostile to potential new users, MAXON decided to time-limit the demo/trial and put it behind a registration.
Personally, I have way more fun modeling and working in Blender now than I ever had/have in Cinema4d. And I am not alone in this... It's a very robust and quite user friendly 3d app. The tabs I really love: quick switching to sculpting or UV'ing with one click. Tabs were something I also loved in Lightwave. The viewport is an absolute joy to work in. C4D feels very clunky to me compared.
Yes, there are rough edges, as there are in any software. C4D is no exception either. The main difference at this point is that Blender is actively being improved making great strides, while C4D seems to move along at a snail's pace. But perhaps with C4D 23 a break-through will finally happen? We can but wait and see.
I believe Cinema4d is losing and/or will lose ground because of its abysmal licensing and pricing, unless MAXON changes it. Compare with Max and Maya Indie (even though it can only be used on projects worth less than 100K) for $250 a year, or Houdini, Blender: all have much more attractive pricing schemes. AutoDesk is feeling the heat, and their response to the Blender upheaval in the market is probably too little and too late. Heck, even LightWave seems to attract one or two new users that would have picked Cinema4D instead, but were rebuked by MAXON's licensing/rental plans. Especially in tough economic times like these MAXON's licensing is akin to a kick in the face when you're already down on the ground.
And exacerbating the situation is that Cinema4D users, while paying a premium upkeep, need to invest in an external particle plugin, external render engine, and other plugins and apps to keep up with the competition. Something needs to give.