It is a way of pampering your lover and showing them your affection. In English when you say 'my dear', 'my beloved' ,' my treasure' ,they are not literally the same words or meaning, but they convey the same message of wanting to display some tender feelings and warmth in a verbal manner. Calling your lover 'enta omri' ( you are my lifetime, the length of time I am alive **Omri here doesn't mean age!!) or 'enat 7ayati ( you are my life) are ways to show them their importance in your life, how you appreciate and treasure them. In a way they are the same for they express and refer to the same feeling ,but literally the words used to express it are different !

''Omri'' literary means= My age!, from Omr= Age. I think they don't use this word in English Hayati : My life from Hayat: Life. Both of them used to praise someone you love, your child or your beloved

你真棒

damian i think there's no difference betwen the both