If you are purchasing exec level rooms anyway, I dont know what else a program would give you other than point earning potential. Since you are paying about $300 per night and about 30 nights a year you should be just about Diamond leve with Hilton as another way to make top tier is to hit 100,000 base points ($10,000).

To be honest, if I was in your shoes I would find out which group has the better properties in the locations that I stay since you are already purchasing exec level rooms.