working in social services, not from personal need.
No denying that there are different pockets in each of the counties. There are plenty of republican wannabe libertarians out in Gresham. And there are plenty of wonderfully progressive liberals in Oregon city. That said Clackamas as a whole seems to come close to 50/50 in many elections, where Multnomah usually comes down more 60/40 or better.
As an example, take the primary elections we just had. Multnomah county had 90k votes for Obama, 20k for Romney. In comparison Clackamas did 28k for Obama and 21k for Romney. And I believe we successfully passed all our school bonds and whatnot. Not that we are perfect, but we tend to be more liberal as a group than most other counties in Oregon. Take Multnomah out of the mix, and I am fairly certain Oregon would be a red state, by the numbers.
Back to my advice.. Working in social services, we found that the county border was a magic line. If you were in Multnomah county and needed assistance, we could generally find some for you. If you were in Clackamas, you were out of luck unless you had friends or family who could help out.
So, my message would be if you don't need assistance to get by, then by all means, move to Clackamas county and help the balance. If you do, then Multnomah county is a better bet for you to be able to survive.