I lived in the Twin Cities for 11 years and then moved to Portland, OR where I've been for 16 years. I'm from the east coast, so I was not a native to either. Personally, I prefer Portland, but that's my opinion.
As a runner, you cannot ignore the fact that it is REALLY cold in Minnesota in the winter and that "winter" pretty much stretches from November through April. It's snowed when I was there in October and May, so I don't think it's an exaggeration. You do get used to the cold, but initially it will be quite a shock. Often winter's days are clear and pretty - BUT pretty tough to be outside. The wind is often from the Northwest and you pretty much have to run towards it (so you don't freeze to death on the return. I got tired of the winter run because it was always the same direction.
(My fingers, toes and ears are still affected by the "frost-nip" I got in my first years in MN). The summer in Minnesota can be hot and humid and there are lots of mosquitos and gnats to deal with when you run in the early evening. The fall is quite nice, but also short.
Running routes in Minnesota, when not snow covered, are pretty good. The River Road and the lakes are always nice, if a bit crowded. Fort Snelling, Hyland Park (great trails) and several outlying parks are great to run.
It rains frequently in Portland, except in the summer when it's typically dry. It's often gray in the winter, but the landscape is always green, which is nice. Things start budding in late February, which was a shock to someone used to Minnesota winter. But Portland has it's share of miserable running weather as 33 degrees and raining can be awful. The fall is nice here, and the summer is glorious.
I'm partial to the trails, so Portland's vast Forest Park is a great place to run. The trails do get muddy in the winter, but never that bad that you can't run on them. There are many loops to create and I never get bored exploring there. Road-wise, there is Terwilliger and the waterfront.
As for running clubs/groups, I'd give the nod to Minneapolis/St. Paul. It's been years since I've been there, but the Twin Cities have much better races and far superior marathon and many competitive clubs. Although the team I ran with has folded, it looks like the club scene is fairly active (RunNFun still exists).
Portland has a truly crappy marathon, very average, boring races and almost no competitive clubs or training groups. Assuming you aren't joining an elite club, it may be tough to find people to train with. If you are really fast, there is a group connected with the Bowerman AC and also there is a small group at Run Portland. For the average runner, there is a club called Red Lizard, but it's focus is not on competitive racers. Imarunr could give you a lot more information on them.
IMO, I thought Minnesotans were actually more cliquish. A lot of people live in MN and never leave, so they aren't exactly looking for new friends since they have so many old ones! It took a while to build a network of friends, but once I did I found them to be a are a loyal and wonderful bunch. So many people move to Portland that being a newcomer isn't unusual. Portlander's are pretty friendly and it was relatively easy to make friends.
I think the public schools in Minnesota are better than the ones in Portland. (I have 3 children) The Twin Cities boasts a lot of cultural opportunities and is better than Portland's (although Portland does have its share - it's just on a smaller scale). The Twin Cities have all 4 major sports, while Portland only has two (soccer and basketball).
It seems like the job market is better in the Twin Cities than in Portland. Houses seem more expensive in Portland. There is great coffee and amazing access to organic food in Portland as well.
I think that both places are great places to live, but there will probably be something that will tip the scales for you. For me, I hate running in deep snow and will put up with rain and mud, so I'm set here. It's a pretty laid-back place and that suits me as well.
Good luck with your decision!