These 2 are completely different - like chalk & cheese!
Kingston is an international kindergarten (Kowloon side) with its own primary school.
寶山 is a local kindergarten (Hong Kong side) with most of its students going to elite local primary schools - mostly to St Paul's Co-ed.
No one can tell you which is better because they lead to different paths for your kid.
If you want your kid to go to an elite local primary school (especially St Paul's Co-ed), then definitely 寶山.
But if it is international schools you want your kid to go to, then 寶山 would be a very wrong choice.
In fact, they probably won't accept your kid if you tell them your ultimate aim is international school!