TL/DR: yes, the organelle has more buttons and an HDMI port.
in the other direction, yes, norns has a bigger screen and (i believe) greater encoder resolution.
besides those, and strictly speaking: no, but it certainly is simpler to run organelle stuff on the intended platform.
they are both linux computers with similar specs, and in a broad sense they will both run the same programs. this requires lesser or greater degree of DIY linux preparedness. contributed projects like mother will require more than the “vanilla” workflow. even the vanilla workflow is (i’m told, and believe) a little less accessible for norns, assuming you want to make patches and not just run them.
probably the biggest functional difference is that the organelle retains the HDMI port of the raspberry pi, and ships with a window system, encouraging you to perform PD patching directly on the device using keyboard/mouse and monitor. norns is more predicated on text-based and networked interactions with the device and is tricker to get into.
the other major differences are form factor. norns has minimal UI elements and encourages each script to have an idiosyncratic interface. organelle has a small screen but more keys/knobs, encouraging a more standardized model of interaction. perhaps one of these simply appeals to you more than the other.
uh: to clarify, the screens are the same resolution, norns screen is literally bigger, and generally scripts rely on it more i’d say.