Go with best sound if you can perceive a difference within the recommended range, but if not, don't be afraid to set VTF at or near the top of the recommended range. Calibrations for VTF aren't always accurate, and too light a VTF will be more damaging to your records than one that's a little heavier, so err on the side of clean tracking ability (no loss of stylus contact) for the most highly modulated recorded passages.
