They are not the same. Harmy’s are a recreation of the original trilogy using the blurays and various other sources such as the GOUT and 35mm film to recreate the original trilogy. The Silverscreen Edition and Grindhouses (ESB and ROTJ) are 35 mm preservations. They have been digitally preserved, but are original without any changes (except for cleanup of the picture due to the age of the film).

Both are true labors of love by truly dedicated fans of the original unaltered trilogy, but are slightly different in how they have accomplished the goal of preserving these original versions.