Hi Goncalo
I use Passata when I run out of Tomato Puree and I water it down about 20%, works fine.
I don't stick to any hard and fast rules, as it depends on the dish and what I have in the kitchen.
My choices are M&S Italian Tomato Puree, because its light and gives good colour.
Any Passata, Any tinned Tomatoes, blitzed and sieved.
I don't use some Tomato Purees, because they blacken a curry, when your cooking, hard and hot BIR style.
A big culprit for this is White Tower, used a lot in some restaurants, because it used to be so cheap. Nothing wrong with it, but not my choice.
cheers Chewy