IMHO If you're mainly a console guy - go the DFC, you will be fastest in an environment you are best used to.
If you're mainly a PT guy, used to mixing in the box, go the ICON.
If you're a console guy interested in flirting with some PT integration, go the system 5.
For TV, I dont think much can currently beat an ICON. Custom groups, templates, PT integration and dedicated dyn/eq section all make for a very quick environment to mix ITB, far faster than the DFC or Sys5 atm. System 5 is getting many ICON features onto the board as EUCON gets updated but the layout is driven by console guys rather than PT guys IMHO - so I dont think it will be as fast for TV though I'm not a sys5 expert.
Certainly tonnes of ICONs in SOHO and throughout Australian broadcasters for quick turnaround TV post.
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I had the privilege of using an Icon back in film school. I wasn't doing any speed mixing back then, but i remember the features of the desk being very intuitive.
Having dedicated buttons for auto preview and write to selection (and within easy reaching distance!) was fantastic for writing automation.
Custom fader groups are great if you're working from a template and want to be able to toggle quickly between your different groups.
Soft knobs for eq/dynamics plug ins also make things more intuitive, IMHO, and can link to most plug ins.
I'm not sure if other desks have similar features, but i'm guessing that some of them are part of the ICON protocol, which is digi only (i think?).