I cant give you an opinion on the Elegant white from Primochill- the reason being that its a fairly new product, and no feedback has been posted on it as yet either, and i personally have not used it (atm im testing the clear ADV).
i would rate the the Mastercleer tubing that i am using as 8/10-ill explain.
Firstly, i don't believe that there is a 10 out there as yet
Secondly, because i have only been running it for a few months-its too early to make a proper call on it, but so far it has been perfect, it has not lost its 'shine', and it was very easy to work with (its very pliable, yet does not kink), i also run my rigs 24/7 so 2 months use, is more or less 3-4 months for normal users (temps are between 24-26c idle, and 36-39 under full load)
The pastel that i am using is perfectly visible without any clouding/hazing as yet.
So that having been said-i would give it an 8 for now, i may well change my mind after another 2 months