new late 2015 imac 27" or 2015 imac 27"

i may be looking to upgrade my 27" mid 2011 imac to a 27" 5k display. Is the newly released 2015 27" imac really worth it compared to if I buy a refurb 2014/2015 5K?

via ehMac.ca http://ift.tt/1MdghMR