I wear a Coolmax Alta t-shirt even when it is warm. The jerseys I have irritate my skin and I find the coolmax alta more comfortable. When the weather is hot the tshirts don't make it much if any warmer but they do take a little of the chill off of a cool morning. Once it get cold I use various baselayers. Fleece seems to do the best with wicking but it is also warm. I havn't tried som of the more expensive fabrics like Powerdry or Under Armour so I can't comment on them.
Craig