Been spending 10 nights ( 5 nights every six months ) in Portland for the last 20 years. Alone, on business.

Observations:
Downtown Portland is much more of a zoo these days. I used to like to walk this very walkable city at night ; I still do, but it's not as much fun and I'm more "on alert" than in the past, which kind of sucks the joy out of it. Lots of street people ( very young, too ) and the cops tell me their hands are tied. So the problem grows. Too bad. It's an otherwise lovely city.
Peak traffic is horrific. And if you're not familiar with the grid -- and the streets dedicated to mass transit where you feel like you're caught inside of a pinball machine -- it can be pretty aggravating. Getting to/fro nearby Vancouver in rush hour? Probably the worse traffic I've ever been in. Worse than LA/405.
Downtown properties have really jacked their overnight parking prices. So the last few visits where I've stayed downtown, I've Ubered in from airport ( maybe $40? ) and used same for a few days to get to appointments. Saves on car rental, hotel overnight parking, being in unfamiliar traffic, paying daily city parking rates, etc... If you use Hertz, there is a walkable HLE on Pine and their rates are usually much better than all the adds-ons from PDX.

Marriott Waterfront
Convenient, especially if you want to launch onto I-5 south. But they got too hoity-toity for my tastes a few years back when they did the whole "Redesigned" thing. (I think after the re-design they added an M Lounge). Walked into my room and saw a thin wooden shelf they called a "desk" and I walked back out, switched hotels and left a message with the GM from the Uber to my next hotel. I guess it was a common complaint and they put desks in now, but judging from the web site pics, they aren't much better. So this property is out of the rotation.

Marriott City Center
Hard to find a more central location. Just perfect. Very small lobby. Weird restaurant set-up for breakfast. Rooms are nice. Not "Redesigned" ( as of a few months ago) . Ask for a corner suite for nice views -- or any of the larger rooms on the concierge floor ( 20) . Here's something odd , though : iirc, ALL the toilets are the tiny round seats not elongated., Is there anyone on earth that has a beef with elongated? Was it just poor planning where they needed that extra 2" for door clearance? I dunno. Weird.
Great restaurants are just a walk from here. El Gaucho steakhouse is one block over -- great happy hour. Portland City Grille ( on top of US Bank building -- 30th floor) has twice daily happy hour and best views in Portland and is barely 3 blocks away. Powell's Books is maybe 7 blocks -- best bookstore in America. And the real keeper is just two blocks away -- Rich's ( old school magazine and cigar/pipe shop).. Treat yourself.

The Nines
It's smack in the middle of Protestville, USA. The lobby is kind of cool. Very "place to stay" with the cool set. Has that vibe. I asked for a room check just to see what all the fuss was about. Clerk showed me a room and I think I could have turned on the tv with one hand and flushed the loo with the other. Felt like I was in a dollhouse. Place is trying too hard. No thanks.

The Sentinel
This is a beautiful hotel. Nice, a little understated, which I dig. Did not stay here, but attended an event here and the ballroom was old school and gorgeous. Didn't see a room. Good location.

Residence Inn -- RiverPlace
Spent a few weeks here with my family. Nice. Once you are there, walkable all around for meals and such. Probably the best option if you have kids.

Residence Inn - Pearl District
Newer property. Very close to Powell's Books. That's enough of a selling point right there. And some hip places to eat and drink, I guess. Not my thing.

FI/CY/RI -- Portland North
These properties are all about 15-20 minutes north from downtown Portland . I might advise staying here if you have business in Vancouver, but not if you are in Portland . As stated above, the traffic is horrific. Usually very cheap here. Access to them is a little funky, but just follow GPS. A few little restaurants ( not that great) are clustered just a walk away from hotels. All fairly new properties. Tight parking, all three properties are a stone's throw from each other. Not for the claustrophobic.

Courtyard - City Center
Another prime location, very near good eats. Stayed here maybe 10 years ago. Once. IIRC, it was a converted office building and still had that vibe to it. Maybe I should give it another shot. Definitely out-of-the-box experience. Tight security. The local area can get a little rough at night ( or these days, during the day).

Courtyard - Convention Center/Downtown
OK, this one is a little misleading. Technically, it might be downtown, but it's on the other side ( east) of the Williamette River and even east of I-5. So if you have a gig at the Convention Center, yes, this is probably a good bet. But if you want to stay in downtown Portland, you can do better.

Hi Lo
Looks hip. Never been. Sorry.

Courtyard - Beaverton
OK, this has been my go-to for the last few years. I get a ridiculously low rate, parking is easy and free ( pretty sure). Starbucks, Einstein bagel, Panda AND a FEDEX store 40 yards away. You're also about a mile away, if that, from a decent mall with all sorts of restaurants. Only real drawback, it's near some train tracks and I guess there is some train noise. Has never bothered me. But you definitely need a car if you are staying here.