Yes, the fine tuning effect of the FM knob when nothing is patched into that input is reversed on one of them.
That confused me when I tried to get them into perfect unison.
Other than that, there’s not really any significant behavioral or sound differences. Some of the controls are very, very sensitive and it can be difficult to get perfect matches in terms of harmonic content. There’s also, I believe, some randomness to phase or something else which means not every note is the same, which you tend to notice more when using them in unison (stereo or M/S or mono). But it can sound very lush that way.