I think both the methods should be roughly equal and the differences you are noticing are because of how floating-point operations work. Due to how floating-point operations work, there can be small differences in the results of the same operation when the operation is done multiple times.
The following resource has more details about how floating-point numbers behave: https://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.html.
But I recommend comparing the output of both the methods with different external sources such as WolframAlpha to determine which method yields a more consistent result.
