What "better suits" can only be determined by a proper analysis of the
business requirements. It might appear to solve the one issue that has
been presented here, but is it the appropriate solution in the wider
context of the whole system? The supertype-subtype model I suggested
as a *possibility* is a well-known pattern that can be used in
situations like this.
Single-Table Inheritance will result in a table with lots of NULLs in
it. You then have the issue of ensuring that the columns for one model
are filled, while columns for other models have NULL in them. On the
subject of NULLs, see: http://www.databasedesign-resource.com/null-values-in-a-database.html
If you decide STI is appropriate for your needs, this might help get
you started: http://rookieonrails.blogspot.com/2008/01/single-table-inheritance-in-rails.html
Or see the Agile Web Development with Rails book, of course.