Both Noah's are the same. I think the problem is in understanding the meaning of the statement in Ezekiel. Noah is mentioned in two verses there. Here they are:
Ezekiel 14:14 Though these three men, Noah, Daniel, and Job, were in it, they should deliver but their own souls by their righteousness, saith the Lord GOD.
Ezekiel 14:20 Though Noah, Daniel, and Job, were in it, as I live, saith the Lord GOD, they shall deliver neither son nor daughter; they shall but deliver their own souls by their righteousness.
As you can see, three men are mentioned. They are Noah, Daniel, and Job. All three are major Bible characters and each of them is known for his righteousness. Noah delivered his family from the flood that destroyed the entire world because of his righteousness. Daniel was delivered from the mouth of lions because of his righteousness. Job's righteousness so impressed the Lord that He bragged on his righteousness to the devil.
Yet, by the time of Ezekiel (which is the time when Jerusalem was destroyed by the Babylonians), the Israelites had become so wicked that nothing could keep them from the coming destruction. Even if Noah, Daniel, and Job, some of the most righteous men who ever lived, were in the land, they would only be able to save themselves.
I understand your problem with Noah. At the time of the flood, he was able to save himself and seven other family members. Yet, the Ezekiel passage states that these three men (including Noah) would not even be able to save a son or daughter. Can the Noah who saved his sons at the time of the flood be the same Noah who could not save a son in the time of Ezekiel? The thing that must be understood is that Ezekiel is speaking of the same Noah in a different situation. It is not that Noah is looked on as having two levels of righteousness, but rather that Noah is being looked at in two different times. The point is that God is more determined to destroy Israel for its wickedness than He was to destroy the world in the days of Noah. What Noah was able to do at the time of the flood he would not be able to do at the time of the Babylonian conquest. This is a statement about the greatness of the wickedness of Israel, not about the righteousness of Noah.