It's empirical fact that there's been far less doctrinal drift in those Christian groups who revere Sacred Tradition than in those who claim to follow "the Bible alone".
Compare what LCMS Lutherans believe with what Seventh-Day Adventists believe, on the one hand, then compare what Roman Catholics believe with what Eastern Orthodox believe, on the other, if you don't believe me. Rome and Constantinople have been separated for almost 1000 years.
"It's empirical fact that there's been far less doctrinal drift in those Christian groups who revere Sacred Tradition than in those who claim to follow "the Bible alone""
Doctrinal drift from what? The teaching of the early Church? That would be something you would need to prove. Protestants base contention is that the RCC has drifted from the simplicity of the early Church.
"Compare what LCMS Lutherans believe with what Seventh-Day Adventists"
Bad comparison. There are a large number of Protestants who believe SDA to be a borderline cult.
"on the one hand, then compare what Roman Catholics believe with what Eastern Orthodox believe"
You mean differences like: Papal infallibility, immaculate conception, development of doctrine, original sin, purgatory, the filioque, equality of bishops...
http://www.ocf.org/OrthodoxPage/reading/ortho_cath.html