Not surprisingly you will get a lot of biased information depending on wether people will actually buy a new MacPro or want to stick to their iMac.
After having worked with maxed out 2013 iMacs for some time and having been able to do some tests with a new MP recently the only thing I can say is: if you primarily use your system for working with FCPX, Motion and LogicX you definitely will see a lot of benefit using even a mid-level new Mac Pro over using the latest and greatest iMac.
If you also do a lot of other stuff it depends mainly on what you are doing. Here's some comparison tests running both systems on a variety of applications:
I second rgilman's links.
iMacs and your MP are a fine machines and if they meet your needs, then save your money. If not, then the new MPs offer dual GPUs, PCIe3 flash drive, 6TB2 and 4 USB3 ports, HDMI and many other improvements not to mention being quiet and cool. Ronny is coolest(nicest) kid on block by definition. Start by what type of work you are doing and throughput/job requirements.
You could also install a second GPU in your 2010MP and see rendering/effects/export improvement speeds under Mavericks, FCPX10.1 and Motion5.1. If rendering is your issue, this might offer a significant speed increase at relatively low cost.
Everyone should be aware and careful on how you use the TB ports in the new MPs as they are controlled and limited by only 3 controllers so make sure you balance the loads over the controllers not just the ports.
See this controller layout…http://images.anandtech.com/reviews/mac/MacPro2013/tbportmapping.png
Hope this helps, Greg