The Gemara often introduces a braysa by using the term "Tanu Rabanan" or the term "Tanya". Assuming there is a difference, what is the difference?
Rav Sherira Gaon, in his letter: Braysa's that were verified by Rebbe Chiya and Rebbe Oshiya are introduced by the words Tanu Rabanan. Other braysos are introduced with the word Tanya.
Rama Mipano, Shu"s siman 25: Tanu Rabanan braysos are generally accepted by all Tannaim, Tanya braysos are the position of an individual.
Professor Chanoch Elbek took issue with Rav sherira Gaon's principle because 1) The Talmud Yerushalmi does not use the term tanu Rabanan, only the term "tani", 2) Meseches Nedarim only uses the term tanya, not tanu Rabanan, 3) Braysos that are introduced by "tanu Rabanan" are then referred to using the term tanya. (From Professor Elbek's book Mavo LeTalmudim. You can see the excerpt here.)