Pine and fir (and oak) were the backbone of 20th century North American lumber supply. This makes them readily available now, as structures from that time period are now being taken down or revamped.
Fir is more subtle than pine in that the color and grain are more consistent across a larger area. Fir has a notable “tanned” color that helps create an elegant, calm look across a larger area.
Pine paneling has a little more character. The grains are more contrasted against the softer wood in between. Pine stands out a little more than fir due to the wider color variation across boards and the less subtle grain.
Which one you want will depend on the larger design you have in mind with your project.
We supply reclaimed wood paneling in these wood species in a full range of dimensions, given their relative abundance.