I'm sure John D will be able to correct me on this but my father used to do a lot of work in Switzerland, the chaps over there always used to say that the watches with the best movements were Rolex, IWC, Patek and Cartier. Most of the other companies had movements made by AWS (I think?) so Tag, longines etc are all quite similar on the inside, just different outers!
Pretty much spot on, apart from Cartier. They use the generic Swiss ETA movements too (not AWS). Most Swiss watches like Brietling, Omega, Cartier, TAG, Longines and even Panerai use ETA movements. Only a few manufacturers truly have an in-house movement and they truly are top top end. Omega are trying hard though with their co-axial movement, but most of their models still carry the old ETAs.