In my humble opinion, one of the better interactive viewers for 360X180 panoramas is the DevalVR viewer, available here:
and demos here:
It is small and easy to use allowing pan, tilt and zoom with the mouse buttons/wheel. I have been using it for years. And you can create an executable file with the image imbedded, so it starts with a single click (automatically starting to pan after a preset number of seconds if no mouse interactions).
On the downside, some mail and file sharing programs will not allow the sending of executable files because of the risk of malicious code.
Mike