Milford Sound is the more dramatic of the two fiords, with Mitre Peak a magnet for photographers who want to capture the beauty of the sheer cliffs that rise so dramatically out of the still waters. A 1 or 2 hour cruise is the best way to capture the feelings of remoteness and tranquility at Milford Sound.
Doubtful Sound is less accessible to visitors and offers a more gentle and serene environment, best experienced in an overnight cruise. It's possibly one of the quietest paces on the planet, with breathtaking forest covered landscapes, waterfalls and viewings that include seals, dolphins, penguins and other marine wildlife.
Your choice will often come down to time you have available and if you have the time, our advice is to enjoy the overnight cruise on Doubtful Sound. If you don't have the time, Milford Sound, including the spectacular drive to get there, would also be a great choice.
And there's a third option - consider doing both!