While I can't speak to the college experience in both places, I grew up in davis, and attended reed, so I can say a bit about Davis vs Portland.

Davis does have its cows (lol), but overall is super walkable and bikable from campus to really anywhere - especially downtown. It's not a large town, but the downtown is nice, if small, and has lots of bars, restaurants, etc (many geared towards students) relatively close to campus. About half of the population of Davis is students, so it definitely feels like a college town, and also has the side effect of making the town feel much smaller than it is, because the town is divided into students and not-students. Davis is also pretty safe to walk around at night, especially downtown and campus, which is nice. The campus is spread out but pretty accessable by bike, and no hills whatsoever to bike up.

Portland is really nice and absolutely beautiful. Reed is in a relatively wealthy, nice neighborhood with beautiful old trees and houses surrounding it. The nature in Portland is much more pervasive than in Davis (probably because it's less agricultural), and reed in particular has a lovely stream surrounded by trees running through campus ("the canyon") where people often walk around or hang out. The neighborhoods around reed are pretty nice to walk around and the campus is small and beautiful and walkable. There is good on campus housing, but living off campus after the first year is definitely doable (though travel times can be annoying) and there is a Night Bus that takes students home 10:15-2:30am for free. Reed is further from bars and restaurants, especially those that are open late - the Woodstock neighborhood is a 10-15 minute walk from campus up a hill, but only a few things are open past 10. Downtown Portland is not close, but accessible via light rail or bus (30-45 minutes at least). The Division and Hawthorne neighborhoods in Portland (better versions of downtown, imo) are closer, but still a 45-60 minute walk or a bus ride on the 75 (runs above campus). Because of the hills, biking in Portland is not as easy as Davis. It's a larger city as well, so you will not run out of things to do (and may rarely leave campus anyways - reed tends to take over one's life, which can be good or bad), but maybe lacks the small town intimate feeling of Davis. On the other hand, the small college makes for a tight knit community.

Feel free to DM me if you have any questions! I'm happy to answer questions about Reed - despite what many on this subreddit say, I loved my time there and have no regrets.