I've landed at Hillsboro, Troutdale, and Pearson as a regular visitor and for business.
I usually don't rent a car. Public transportation is good, the rentals aren't cheap, and Uber or Lyft usually works well.
If you land at Hillsboro you can take the Max blue line train to the Rose Quarter station, and then walk to Moda. It's most of an hour train ride and maybe a five minute walk. Hillsboro sits a little higher in elevation than the other two, and is ringed by higher terrain. On a day with low ceilings it makes a difference. There isn't much going on that far out in terms of entertainment or interesting places to eat.
It's hard to get downtown from Troutdale on public transit. Either a long bus and/or train ride, or a long cab ride. The winter wind out of the Gorge can also howl on an ugly day, as it sits right where the Gorge narrows.
My first choice would be to land at Pearson and take an Uber or public transit downtown. Generally Portland Approach has me arrive low, and creep around to the Northwest of Pearson. Occasionally if PDX traffic is light I get cleared through PDX airspace north of the river to depart eastbound. Watch your altitude, as the airspace ceiling over Pearson is 1100. Read the Pearson special instructions below.
https://notams.aim.faa.gov/lta/main/vie ... 0330964778We usually stay in either the Pearl District or NW 23rd. Lots of great restaurants. Salt and Straw has ridiculous ice cream.
On the way back, the WAAAM museum on the airport in Hood River is incredible, and keeps getting bigger. Perhaps 200 antique airplanes and autos.