Choose dimensions for the actual placement
EPS artwork can scale, but a PNG is fixed at the pixel dimensions chosen for export. Estimate the web or document placement first. A small raster may blur when enlarged; a needlessly large one can increase page weight and storage.
If the graphic is used at more than one size, export from EPS for each intended role instead of repeatedly resizing a previous PNG. Keep the source and record the dimensions. The target should determine the pixel count, not an arbitrary maximum setting.