Ask anyone in the landscaping trade around Portland what the single highest-return job is and most will say bark. Fresh bark dust makes a yard look finished in an afternoon. But the reasons to do it have more to do with the Oregon climate than with looks.
In winter, mulch insulates roots from the freeze-thaw cycles that heave shallow-rooted plants out of the ground, and it keeps heavy rain from compacting bare soil into a crust. In summer, two to three inches of bark cuts evaporation dramatically, which is the difference between watering beds twice a week and every day.
It also smothers weeds. Seeds need light to germinate, and a proper mulch layer blocks it. The key word is proper: an inch looks fine but does little, while four or five inches can suffocate roots. We spread at two to three inches, keep it a few inches away from trunks and stems, and refresh annually as it breaks down.
Fir bark is the Pacific Northwest standard and holds its color well. Hemlock is finer and softer, popular for play areas and paths. Dark dyed mulch gives a modern look but fades faster in full sun. Whatever you choose, edge the beds first so the line between lawn and bark stays sharp.