I guess it depends how you think about it. Looking at it in-game though, Toph is so pissed she hits you in bk4 love. In slave shes annoyed but still teases you. Then Katara and Toph still get along great so they had eachother for support at the least. Anyway I didnt mean to say they arent heartbroken in slave but they are hurt less.The slave routes have you psychologically break someone into submission until they need you like a drug.
Then you leave them.
I wouldn't really say it's better.
Well have to see how Korra is at the end of bk4 love but in slave she was hooked up with Asami already so she wouldnt miss you as much.
Bk2 is a mess, but its kindve funny picturing Zuko coming to after you banged his sister..