Uesegi indeed are the best, imo.

They come from a very rich area with a huge amount of Koku as well as mines;
They get Shinano, which can support an armoury, has +1 CAVALRY(!) and is rich;
They get Archers cheap, almost as cheap as Yari Samurai.

Their ability to field entire armies of Samurai of the Kyu and Yari early on means they are deadly to anyone who is stuck with Ashigaru! The only problem for them is the fact that the nearest clans are also pretty well off, with Takeda, Hojo* and Oda not very far away...

*Hojo seem to mind their own business and then trash you out of nowhere.