I really like the look of Christmas Moss too but i can't get hold of any. I like Moss Balls too but have no room lol
I think it mostly depends on the look you are trying to aim for in your tank, and which of the mosses (not the balls) you like the look of because their leaves are all different shapes
There is no best moss. It's down to personal opinion.
Also, moss balls aren't moss, they are a form of algae.
Moss will thrive if given enough flow and trimmed well. Nutrients and CO2 will speed up growth and make it more compact too.