hubiera vs. hubiese

Whenever I have used "hubiera" speaking with people from Spain, they invariably repeat (or correct) my phrase using "hubiese". Not so with those from Latin America. Is this a regional thing between Spain and the Americas?
 

Apparently there are two imperfect subjunctive tenses which mean the same thing.  Also, the -se form (hubiese) is more traditional but is being replaced with the -ra form (hubiera).  Perhaps the people in Spain are clinging to the traditional form.  Here is an article which discusses this point:

http://spanish.about.com/od/verbmoods/a/2impsubjunctive.htm
 

In the Spanish course I took in Peru, my instructor said that those two forms are interchangeable and it's the speakers preference on which to use.

Hola a todos,

Here is an example from the LIGHTSPEED folks using both forms in one sentence.  Fuera cual fuese  su razonamiento, el plan no le salió bien. Whatever his reasoning was, the plan didn't work out well for him at all.

Saludos,
Ricardo

Thanks, all, for your comments. I had thought, incorrectly, that the difference might have been due to Spain vs. Latin America. It's easy to come up with wrong conclusions when you generalize from a limited set of experiences.