Large feature classes may perform slower as file geodatabase feature classes than they do as shapefiles.
A file geodatabase can become fragmented, causing performance issues. Running ‘Compact’ on the geodatabase greatly improves its performance; however, in an unsymbolized draw, redrawing the shapefile may still be faster.
When using an attribute value for a symbolized draw, file geodatabases usually draw faster than shapefiles.
To maintain a high level of performance, periodically right-click on the geodatabase and select 'Compact'.