Both mean the same, there is absolutely no difference between these two forms in meaning. The only difference is in perception. Hubiera, tuviera, quisiera are a lot more common in the spoken language, in all Spanish speaking countries (so the difference is not regional), the form hubiese, tuviese, quisiese are usually used in written language. So, when someone uses the latter in conversation, he may sound either 1) more educated, 2) cocky. That will depend on the scenario, if it is used during a business meeting, it is taken as most respectful towards the clients, if it is used with close friends in a bar during a philosophical conversation, it might get a joke on the "elevated usage of the language", but nobody will feel offended or think that it is "a display super ego", but if you use it in a bar with people whom you just met... it might be interpreted as that.

Los dos valen, lo que pasa es que se oye más "hubiera" que "Hubiese" según la región ejemplo: si yo hubiera/se...........................................