They're both good yanagis. The Masamoto has nicer finishing of the blade but I actually prefer the Tanaka because he uses better steel. http://www.chefknivestogo.com/tanakabasic.html
I also really like the fact that Shigeki Tanaka runs a small business with just a few employees and controls the entire process from heat treating to shaping and finishing his knives. They're excellent values.
A third knife you should consider in the price range are the Kaneshige yanagibas. Love those knives. Great work at this price level.