Over the past ten years, I've installed all types of flooring and have seen all kinds of quality levels. The wood the Silvas chose for the Billerica house is among the best we've used. Hardwood comes in several different widths and grades.
Select oak has a bright grain, a few flaws, and most pieces match well.
Common has both light and dark pieces with some marks, while Number Two Common has all sorts of character marks like knots, worm holes and discoloration. To produce quartersawn lumber, a log is quartered and then awled perpendicular to its growth rings, producing narrow boards with great dimensional stability and attractive vertical grain. It will expand and contract much less than plainsawn lumber. Because of this quality, quartersawn oak is an especially good choice for installation over an in-floor radiant heat system such as the one used in Billerica. Grade for grade, quartersawn lumber is more expensive than plainsawn because of its slow milling process and the amount of log that's lost in the quartersawing.