I've done Doubtful once and Milford three times. Milford is much easier to access and therefore less expensive. Doubtful is much more remote, accessible only by crossing lake Manapouri by boat, taking a bus over Wilmot Pass and then boarding the cruise. It takes an entire day and is quite expensive.

I enjoyed both, but would have enjoyed Doubtful a lot more if the sun had been out - don't believe what that they say about waterfalls making up for lack of sun. There's nothing better than a clear sunny day in the sounds, but they're infrequent.

The advantage of Milford is that you can combine the cruise with some serious exploration of the Milford Road, which is almost better than the sounds IMO. You can walk to Key Summit (beautiful on a sunny day), visit all the overlooks and pullouts, take several nice walks, etc.

Don't forget that Milford is a four hour drive from QT and Manapouri (starting point for Doubtful) is about a two hour drive.

Thanks Melnq8. We are not driving but joining one of the tour coaches. If we go to doubtful sound we have to take Relaxing journeys from QT and back to QT. If we go to milford sound, we have more choices of the tour companies.

The problem is we need to book before we leave for NZ which is in 3 weeks time and we wouldn't know if that day would be a sunny one or not.

Yes, it is much more expensive to go to Doubtful Sound. Is there a big difference in scenaries between the both of them? I have heard the doubtful is less crowded and more peaceful whereas milford sound is very crowded and touristy.