Stayed at Acadian Mansion from 4/5 to 4/9. All mansions were open.
Magnolia Mansion can be treated like a hub because the bridge connecting the island (where the big pool is) is located in the rear.
Acadian and Oak Manor flank Magnolia and would be a good choice too. The walk from Acadian to the pool was 5 minutes. The walk to the lobby is a little longer but doable. The walk is very scenic. The other mansion Pratere Place is a long walk to the pool but closer to the lobby.
A first floor river view room may not offer a good view due to the shrubs around the mansions.
Acadian and Magnolia share a small pool that can be refreshing and is only a short walk from the building.
The complex looks daunting on a map, but I was surprised how compact the site is. There was plenty of parking with adequate nightime/security lighting.
By advised that not all buildings have elevator access, but I think the tallest buildings have only three floor.
Finally, AB and mansions seem to offer the same amenities. It's important to be close to the bus depots. Acadian is close to the north depot which is the second to the last bus stop. Getting a nightime bus to magic kingdom was a problem for me because the buses were full. We ended up taking an Epcot bus and connecting to MK via the monorail. Just have a backup plan prepared.
We chose POR as our first WDW resort too, and we enjoyed it. The pros are the landscaping, cleanliness and the boat shuttle to downtown disney. The biggest con is the bus transportation. It seemed that the return lines to POR from the parks were longer than other moderate resorts. MK transport can be a challenge during peak times, but buses to the other parks were fantastic.