Haven't seen an Isaac Blue in the flash yet and its kinda too late now as my build week is confirmed so its Indium for me. Still look at my Pure White GTD after 3.5 years and think its a fantastic colour but another 2 years of white is maybe too much. Certainly is for my wife who drives the car everyday. Do regularly see an Indium GTi locally which is generally very dirty and doesn't look great, I am consoling myself by saying my car will be spotless and hopefully the colour looks a lot better clean.
You will be pleased with Indium, it looks fantastic on the GTI, especially when clean but is actually good at staying clean. Longest I left mine was over 2 weeks recently due to an early new arrival in our household but it does stay looking good.
I parked next to a Carbon Grey MK7 recently which shows off the difference nicely as Carbon is much darker and also was next to a Mk4 V6 4Motion the other day which the lady has had almost from new, makes the Mk7.5 look pretty low from the back compared to the Mk4. I've gone for black GTI badges which much prefer to the std silver.

