Hi, it's me again: I haven't cruised HAL but have the other two lines. Both have positive and negatives as in any line: NCL and the Sun:
Very lovely ship. Of course only a few years old (about 2 now) Freestyle is just what the doc ordered for our family. Some do not like the concept; I almost can't imagine anything better. The alternative dining is superior and the main dining is good to very good. The entertainment is consistantly voted the best or almost best at sea. NCL crew normally are very friendly. The cabins on the Sun are standard to a little larger than standard in size with good storage. The negatives and I say that with tongue in cheek cause I don't really think there is much negative: the service in the main dining rooms are not quite as good as it was many years ago. This could be due to automatic tipping system, freestyle or just the age we live in. The buffets were very average, but I have heard there have been changes and they have improved, pool area very crowded on sea days, much more so than any line we have cruised. All lines have some problems, NCL the worst.
RCL: I haven't been on the ships you are talking about so can only give opinion based on my experience with the 2 ships I have sailed: Very lovely public areas; nice pool area, good food and good entertainment. Lots of activities if you are into rock climbing etc. The staff on our two ships were a mixed bag. We had very good, average and bad service. The buffets left us totally cold. The cabins were small, but very clean and well layed out. The ship seems to devote much of the ship space to the public areas.
HAL: all I can say is based on what I have heard and read. The service is wonderful, the food used to be great, but think it's gone downhill somewhat. The newer ships are beautiful I have heard, but the older ones are pretty sad. The age range as you may know is on the older, much older side. HAL is trying to shake the image as a line for the retired only, but doesn't seem to be doing a very good job.
Depending on your age and interests I would lean toward NCL or RCL. Of course I have to admit I am a strong supporter of NCL>
Just my opinions,
Nita