We have a BB and a Buba Sling.

We bought the BB whe we were expecting, thinking it would be the right thing, once DD was big enough for it (supposed to be 3.5kg, she was 3 months old before she reached that weight... it worked really well for us for quite a while.

We were given a buba sling when she was about 4 months old, and she hated it at that stage.

Eventually she loved it and still does!

I went to use the BB when she was 10 months old and 8.5kg and hurt my neck/upper back, requiring 3 physio sessions to put it all right again

I really really really wish I had bought a sling earlier, for the next bub we are planning to try a HAB or another similar sling

So from someone who has used both.... the sling wins