right, so in effect what youre sayin is the higher the level of 'co-polymer' the stickier it is and the less 'sand and cement like' it is...
in other words, a product with a high level of co-polymer will virtually stick to anything. alright, anything reasonable such as polystyrene or even cellotex, wheras the cheaper versions have less co-polymer and are therefore more suited to substrates with a bit of good old traditional 'suction' to hold em in place?
you wouldnt want to stick anything at all over timber or say 'upvc' same as just about anything in the plastering world yes?
but given a reasonable amount of play, and a high level of insulation, what you want is a product particular to the amount of movement expected, and the better the product, the lower the risk of things like shelling, delamination etc yes?