It's hard to compare the two. I've played so many great games from both, and many buggy ones from both. If I was forced to choose I'd most likely choose Bethesda. There is no game like Morrowind that is as old and still as good as it is.

Loved BioWare for Dragon Age Origins and 2, but I hated Mass Effect. Couldn't barley get through it.

Mass Effect is the games which tip the scales to Bethesda.