A merino long sleeved layer has the benefit of being considerably warmer than a poly/pro long sleeved layer, can be worn for about 3 consecutive days before odour becomes an issue and can usefully serve as an extra warm layer in a cold dormitory. The drawbacks would be that it takes considerably longer to dry when washed and is a fair bit more expensive to buy. Perhaps carry 1 merino long sleeved top and 1 long sleeved poly/pro top. I would avoid cotton layers totally, they are a very poor insulator when wet, take a long time to dry and heavy compared to wool or poly/ pro layers. Have never come across nylon layers other than as a component in rain jackets so no useful advise to offer.
This link gives advise which my personal experience of multi season hill walking in Ireland supports:
http://besthiking.net/comparison-of-base-layer-materials/
In order of affinity for water/ sweat wicking cotton is greatest,then wool then nylon and polyester.the inverse applies to ease of drying,so for eg polyster is quick drying and slow to adsorbe sweat,and mist.In hot external ambient air cotton cools best due to acting like an outer sweating skin if it is loose.polyester has best air retention and concequent best heat insulating properties but if the external air is hotter than comfortable or if your body has to dissapate heat polyester is the poorest at this function.loose cotton or wool is used by desert dwellers,not cheaper nylon,polyester of acrylic.