Here is how Ethereum and Polygon Matic have performed over the last 6 months
September: Polygon Matic +0.4%, Ethereum (-0.8%)
August: Polygon Matic (-2.2%), Ethereum (- 3.5%)
July: Polygon Matic +93.4%, Ethereum +48.6%
June: Polygon Matic (-23.1%), Ethereum (-13.4%)
May: Polygon Matic (-45.5%), Ethereum (-44.3%)
April: Polygon Matic (-35.2%), Ethereum (-18.3%)
While there appears to be a degree of correlation in terms of the direction, the magnitude is not the same. A combination of the two is good for risk management