Hey Rick,
A SATA disk is just a disk, not Fusion (which would be part SSD and part disk).
You'll see a dramatic improvement in launch times with an SSD. And, the new iMac's SSD is much faster than that in the 'new' (2013) Mac Pro:
http://barefeats.com/imac5k12.html
An overview of the updates in the new iMac 5K:
http://barefeats.com/imac5k11.html
See also:
http://barefeats.com/imac5k16.html
and other recent tests there.
(If Apple were to release an updated Mac Pro with faster memory and SSD, then another option for you would be to use your iMac as a monitor for a Mac Pro with even more cores. But, the current Mac Pro is out of date technologically.)
Karl
PS If you've not updated to El Capitan, you can use your 2011 iMac to run older versions of AC...
Also, you can use your 2011 iMac as a second monitor to your new Mac with "Target Display Mode":
https://support.apple.com/en-us/HT204592
One of the forum moderators
AC 28 USA and earlier • macOS Sequoia 15.2, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB