They taste less sour as well as sweeter and stronger the a orange. 

tangerine is firm to slightly soft, and pebbly-skinned with no deep grooves, as well as orange in color.

Tangerines contain 85% water, 13% carbohydrates, and negligible amounts of fat and protein (table). Among micronutrients, only vitamin C is in significant content (30% of the Daily Value) in a 100-gram (3.5 oz) reference serving, with all other micronutrients in low amounts.