Well, pretérito perfecto is frecuently used in sentences like "hoy he visto un accidente", "¿has visto tal película?"
There's no diferences between 'hubiera/hubiese', 'amara/amase', 'tuviera/tuviese'... The '-ase/-ese' form comes from the latin '-(v)isse'. Example: amavissem, (I would have loved). In Spain the first form is more used than Hispanic America, where is considerated more formal.