If you can find a difference (aside from markings on the tablets) the FDA would be VERY interested in hearing about it.
Generic drugs are supposed to be the exact same thing as the brand name. I've taken nothing but Teva brand generic estradiol with no issues. Due to some delays leading to being bored at work, and being on good terms with a customer I've taken an afternoon in a lab to separate out the components in a portion of a tablet and run them through a fancy NMR spectrometer. It's most certainly estradiol and fillers just like Estrace is supposed to have.