non-ActiveRecord model structure through api calls

This question is more about strategy than a how-to.

I have MyApplication which interfaces with ApplicationX through xml-rpc
calls. In MyApplication I display information from ApplicationX. This
information are from classes within ApplicationX.

Currently, I continue to go back and forth with the best way to approach
this. Do I:

- replicate the information into MyApplication and deal with syncing
issues. The pros I see with this route are easy validations,
ActiveRecord associations, RESTful urls, etc..

or

- just make api calls whenever I need the information and deal with
non-ActiveRecord models. The pros I see with this option is not having
to continually sync the data with ApplicationX.

or

- Is there a way to do both? Create ActiveRecord models with an xml-rpc
connection instead of MySQL connection. Is this possible?

I guess I'm wondering the best approach to take with the described
senario. Any tips?

Have you looked at ActiveResource ? (assuming you own application X
and can change it)

Fred