PDX enplanements in 2015 were 16.8m passengers, ORD's were 76.9m passengers, so I don't think the former is a terribly pertinent model for the latter. PDX is geographically peripheral and hosts just 17 passenger carriers. O'Hare is a national crossroads serving about 45 airlines, not counting cargo, and AA and UA both hub there. Most of what people like about PDX (lack of congestion, cozy layout, short gate-to-gate walks) is not reproducible at a high-traffic transfer terminus like ORD.