Drawback is that power budget HO is available towards the cells from the other band.
This can be seen as an advantage as well, obviously.
Confused ? You should be !
It all depends what you want to do with your network. In my own strategy for multiband network, I disable this parameter so that HO between cells 900 and cells 1800 are done thanks to capture HO and emergency HO. No PBGT HO whatsoever.
But really, it’s up to you.