Many people tend to confuse Pine and Douglas Fir. This is understandable because both are softwoods harvested in the northern hemisphere and are used extensively in the building trades to provide lumber and plywood for homes and as a base material for cabinets, flooring and other woodworking projects.
While both have their merits and are excellent choices for a variety of projects, there are some differences you should be aware of when considering the type of wide plank flooring you may want in your home:
Grain: wood grain is an excellent indicator of overall stability. The closer together grain lines are, the more strength and stability there is to the wood. Pine tends to have broad grain lines that wander, and if not properly prepared and dried the soft wood between those grain lines may expand and contract, causing cupping and twisting. Douglas Fir on the other hand, features a tight, flowing grain pattern that resists warping and twisting.
Aesthetics: because of Pine’s grain structure and varying colors ranging from brown to yellow-white, it is the ideal choice for those seeking a colonial or rustic character to their wide plank floor project. Douglas Fir on the other hand is quite uniform in color (a dull-yellow) and grain and is ideal for a contemporary setting. A Douglas Fir wide plank floor features a beautiful flowing effect that is absolutely stunning. And because of its incredibly uniform appearance, it readily accepts a wide variety of finishes with great consistency.

L to R: Pine and Douglas Fir
In the end, both woods are excellent choices for your flooring project; it just depends on the look you are trying to achieve.