Balsam fir timber is much softer than white or black spruce. Fir has flat needles that can't be rolled between the fingers, and the needles are generally arranged in a flat plane. Spruce needles are fairly equally distributed around the twigs and are more square / rounded and come to sharp points at the tips.
Spruce tends to have rough heavier bark on the trunk, fir smoother. Balsam fir and possibly others have sap pockets / blisters in the trunk bark that can be popped with a pocket knife. Fir seems to live a shorter life, maybe 65 - 75 years, spruce in good conditions may live much longer.