i havent caught up to "Tell me that you love me" yet,i have finished until the 8th episode,i have watched Aishiteiru to Ittekure and they are very different drama,in "tell me that you love me" the leads are both similar and "heal" each other while in the japanese version the FL is a young cheerful woman who pushes the ML to be better.
Objectively and subjectively i suggest the Korean version,although i love older Jdramas "aishiteru to ittekeru" left me disappointed.I would still recommend watching the Japanese version as ultimately they are different.