jhead Comment v. EXIF ImageDescription

I apologize for opening another thread on a topic that seems to be have been somewhat overworked, but I have been running into to some issues and have not found good solutions in the forum, primarily because several of the recommendations seem to be based on previous versions of Gallery (viz., not 1.4.4).

When I use jhead to append a comment to a JPEG header, it shows up in two fields: COM marker comment and Comment. While Gallery is able to read this data, it does not seem too keen on displaying it easily. On the other hand, if I edit the metadata in Photoshop CS, it goes into the field ImageDescription and is then displayed under the photo in Gallery's album, so long as I uploaded it through Gallery Remote.

My question, then, is how do I change the configuration of Gallery to display the field Comment rather than the field ImageDescription ? Or, alternatively, how does one call upon jhead to add to a field ImageDescription, rather than Comment?

Related to this, and if both avenues present themselves as a solution, which would be better to have attached to a picture--the ImageDescription or the Comment metadata? Which set of metadata is searched better in Google? Which set is more generally able to be read by the widest number of applications? Is ImageDescription considered an EXIF tag?