Coeur d'Alene Id to Biggs Junction. Or

Almost the same mileage either way and almost the same est time. 14 is a smooth, relaxing drive, but is 2 lane and has truck traffic just as 84. I prefer the WA side myself, and traffic is usually less. If you have never taken 14, go that way!! You'll like the view from the north side of the river!!

Is that 182 or I82? I90?

Are you taking I90 to US395 to I82, and then debating whether to leave I82 on the Washington side and take WA14, or continue to I84?

Probably a toss up. Terrain is basically the same - open scrub land, and both highways are flat and straight. Being freeway I84 is probably a bit faster, but the difference will be minor, especially on that long of a day.

It's west of The Dalles that the Gorge becomes more scenic, and views from the Washington side complement those from the Oregon side.

There's nice camping on the the Washington side of the river at US97.

I drive that leg pretty frequently. I like the WA side when heading west bound. I usually decide pretty close to the cut off for Hwy 14. If there is a lot of truck turning off then I go to Oregon. Now that Oregon raised the speed limits Hwy 14 seems to have a tad less traffic, but keep an eye out for the cars that will want to pass you, some take some crazy risks.

One possible route is I-90 to 395, cut down 395 all the way to Pasco and Kennewick, then onto I-82 down to the Columbia River. Then you can turn off and take 14 west all the way to Biggs. Alternatively, you can cross the river at Umatilla, and take 730 through Irrigon to Boardman, or just drop down I-82 until it terminates at I-84 and head west to Biggs. Oregon side is faster and has more services along the way (and mountain goats along the basalt cliffs between Arlington and John Day Dam).
Steve