Would be nice to get a real answer here instead of the snyde remarks...
Two Gold PSUs are a very cost effective way to setup a mining rig, 1200w PSUs are very expensive.
So, let's try this again...
The Add2Psu as I understand it will turn the 2nd PSU ON AND OFF in sync with the first.
The interconnect cable may only turn PSU #2 ON, but maybe not OFF?
I haven't tried this yet, just about to setup my rig and I want to use the right part for the job.
Don't bother replying if you have nothing useful to add.
Add2PU is a relay device; meaning it will power on and off the second PSU and keep it in the same state as the first PSU.
Interconnect cable is more for a motherboard which will send the power on signal to both devices. While it performs a similar function, it will not relay the power state between the two power supplies and it's possible for one to go off with the other still running.
Generally speaking, it isn't a good idea to mix power supplies but if you had to do it I would go with an add2psu as the relaying of power on/off would be more reliable than just using an interconnect cable rigged to always be on.