What's the comparison here? Just from the Wikipedia pages (and just the allied side),
Exercise Tiger:
749 killed ~200 wounded 2 LSTs sunk 2 LSTs damaged
Operation Overlord:
United States 124,394 casualties; 20,668 killed United Kingdom ~65,000 casualties; 11,000 killed; 54,000 wounded or missing Canada 18,444 casualties; 5,021 killed Poland 2,097 casualties