Letizia: Either way I think is fine! She had a more youthful look with the longer hair and now her hair seems to be more serious. Not that there is anything wrong with that but it's just very simple and blunt. Over a long period of time I'm not sure Letizia's current hair is going to be all that exciting.
Mary: I never really liked the long hair that she had when she first got married. It was always fixed nicely but it just makes her face seem so long. The short hair was fine but I little too dull to last a long time. Therefore, I prefer her current medium length hair that she has right now. She has plenty of layers to add excitement and yet it's long enough to do up nicely.
Mette-Marit: I think I prefer it longer. She has this little kid look to me when she gets it cut a little above the shoulders or a little under the shoulders. I think I say this because her hair is always cut so bluntly, little to no layers. If they would cut her hair to have an overall shorter length but add some movement with some nice face framing layers it wouldn't look like kids hair. I say a kid's hair because usually little girls don't have lots of layers and things like that in their hair it's pretty much all one length.
Martha-Louise: I have to say both! She is one royal that I watch for mostly to see what new style she has.
What about Maxima?
Long hair:
ANP Beeldbank
ANP Beeldbank
Shorter hair:
ANP Beeldbank
This pic was soon after the birth of Alexia she cut her hair and had bangs.
I think for Maxima I prefer the longer hair. Her hair not always in place which she is criticized for but I think that is somewhat part of her appeal at times. She gets in there and does her job and who cares if a few strands are out of place.