Well I know some people swear up and down that the estradiol in Estrofem is more potent than the estadiol in progynova but I always assumed that it was really due to Estrofem dissolving easier giving effectively a higher dose rather than one companies estradiol being somehow better than another's.
As far as you specific situation I don't really know if there is some hidden difference, I know my spiro is a generic and has a nasty mint taste, which encourages quick swallowing.