Are they both heads or is one a combo?
If both can run independently through speakers already then chorus in front will sound OK but channel switching can becomes an issue.
I generally use a chorus and stereo in/out rack multi-Fx/reverb (it can also take mono in from Fx send and make a big stereo image,
So I use my mk3 as my preamp, I put a chorus and my lexicon rack Fx in the loop. Fx send > chorus > rack Fx (stereo in) > L channel to Fx return & R channel to Fx return of amp 2.
That way my mk3 is the 'master' for gain and channel switching and the power section of the 2nd amp is acting like standalone poweamp. Saved me buying a simulclass 2:50 or 90:90 rack power amp
I don't set it up this way often as moving a heavy combo and my big Mesa cab & an extra amp to a gig is a pain but proper stereo reverb and delays are absolutely glorious when I do.
I've not had any ground noise issues but as mentioned, you need to be aware and I always use an RCD device too.
Luckily my rack Fx had input level controls so I can adjust for the Fx level which can get quite high with my mark 3 depending on settings.
FYI... you can still get a great stereo Fx by plugging that extra output into almost any amp, even a cheap practice amp as it tricks the brain just as good into hearing the extra modulation.