Tough call. Remember if you stay at SOG, you'll need to add $17 a night, per vehicle, for parking. Parking at the theme parks for offsite guests is $30 a day. The parking charges might offset the price difference. Also, I know the extra hours are tempting, but how old are your kids, and will they stay up for the extra hours? We've found you can either stay for extra hours or get up for rope drop, but burning the candle at both ends is exhausting and not much fun if the kids melt down.
I guess I'd consider how many rooms I need and how much time you'll spend in your room, but I'm thinking POP might be the better choice. If you really can't decide, would you do a split stay? To me, moving is more hassle than it's worth, but some folks really like to resort-hop.