In Disney-speak, "moderate" has a very specific definition.
Disney has three levels of resorts - Value, Moderate and Deluxe.
There are 4 Moderate resorts: Caribbean Beach Resort, Coronado Springs Resort, Port Orleans French Quarter and Port Orleans Riverside.
Similar rooms at all 4 resorts have identical prices.
The major differences between these resorts are the themes. Disney is heavily into theming its resorts. CBR has a Caribbean theme. CSR has an American southwest/Mexican northwest theme. POFQ has a New Orleans French Quarter theme (minus the drunkeness and debauchery). POR has a rustic Louisiana bayou theme.
CSR is also a convention resort, so it has a few things the others don't. It has a gym. It has room service (the others have pizza delivery only). It has queen size beds. It has some Club Level rooms and some suites (the others don't have those options). The rooms have only one sink (the others have 2).
POFQ and POR have boat service to Downtown Disney.
CBR's rooms are slightly larger than the others (340 sq. ft. versus 314 sq. ft.).
Mostly, as I said, it comes down to theme. Choose what tickles you the most. They all are high-quality places, all of them are what you would expect from Disney at this price point.
I hope this answers your question.