From BR Bullpen

The Advanced Rookie leagues are considered to be the Appalachian League and Pioneer League, a step above the Gulf Coast League and Arizona League. The Advanced Rookie leagues play in actual cities instead of being a complex-based system. This enables them to draw in crowds that bring some reimbursement, making them more stable than the complex-based leagues. Additionally, playing in front of crowds helps the players adjust to higher-stress environments, though some feel the GCL and AZL help players develop in a lower-pressure scenario.