Sudoku puzzles with symmetry, easier or harder?

Created with Highcharts 4.2.3 /Highstock 4.2.3Number of puzzles generatedNoneSymmetrySimpleEasyIntermediateExpert0k1k2k3k4k5k6k7k8k
NoneSymmetry
Simple229734
Easy46181920
Intermediate1667225
Expert34867121
Number of puzzles generated
Sources: ostermiller.org