I think you make a good case for the Hameg for frequencies above Instek's spec sheet of 400 Hz. It was good you could get both to read far above their rated specs. Also, the Instek is no longer sold, so in this price range, there aren't too many options, and the Hameg and Instek have similar list prices.
Datasheets for the Hameg say its rated to 1kHz, so its fine for most power readings used commercially.