Both are same. Transmission line also has the radiation but it is mainly intended for low loss and load is 50 ohm. so restrict on radiation , conductor and dielectric loss.
Where as In antenna we need to radiate here we do not say radiation loss. How ever we look for low conductor and dielectric loss
Hence both are same. "The transmission line that radiates is nothing but the antenna" How ever we look the parameters like gain beam width etc. leads in development of transmission line/antenna to meet the requirements. Hence the antenna domain.
There are several type of antennas by mean of radiation method. one type is transmission line type antennas which can be precisely modeled this way. But there are many other types (like antennas who couple to the air by progressively changing the impedance) which could not be modeled easily and precisely by simple TL models.
you can find more information in antenna literature books.