They all have the same amount of protein and sugar.
Isn't quite true...
If you take out the 4% fat, then the liquid that's left has more sugar than the full fat version.
We buy the full fat because it has the lowest % sugar.
I'd get gold top if I could. Even fewer cabohydrates.
All supermarket milk is skimmed, it then has cream added and is homogenised. They're all good- if you're a baby cow.
For the rest of us, it depends what your morals are, and what your goals.
If you want 'all the health benefits' you need unpasteurised (pasteurisation degrades the vitamins) unprocessed (vit A & D are lost in the fat skimming), and I'm not sure you can get that in That London.