Our order of preference for airports is: LGB (Long Beach), SNA (John Wayne), and then LAX.
LGB is the smallest airport, just 14 gates. Getting through TSA takes mere moments (seriously, like less than 5 minutes any time we've been there). Unfortunately, there aren't many large airlines that fly out of there that I'm aware of. We always fly Jet Blue in/out of LGB. A taxi is $45 to the
Disneyland resort area, and about $55 for the way back. Commonly, from PDX to LGB is about $100 each way. A taxi ride is about 25-35 minutes.
SNA is a small airport, but not as small as LGB. Many major airlines fly though SNA. We usually would fly Southwest through SNA. Our "great buy" price (again from PDX) to SNA is $150 or so. A taxi from SNA to Disneyland resort area is $40-45 each way. A taxi ride is about 30-40 minutes (I can't remember clearly, as it's been 18 months since I flew into SNA.)
LAX is the largest. Most major airlines fly through it. We found SW and Virgin to generally be the cheapest non-commuter flights here. Flights are usually the cheapest going here, but it's the furthest away from DL resort area. Our "buy price" for LAX is under $120 each way. A taxi is $100 each way, so we won't do a taxi from LAX! We usually do the Disneyland Resort Express (not ran by Disneyland). A ride usually takes 1+ hours (it's been as long as 2 hours when we flew in Wednesday afternoon and hit rush hour traffic.