Victoria Kindergarten and Small World Christian Kindergarten are both great kindergartens. Victoria is a bit more commercial but teaches much more Chinese compared with SWCK. I personally haven't visited SWCK but have only heard great things about it from close friends to edu forums; SWCK having caring wonderful teachers and all.
Beside the kindergarten itself, you may also want to consider the future primary / secondary schools they are affiliated to:
Victoria -> VSA (Victoria Shanghai Academy)
SWCK -> ICA (Island Christian Academy)
VSA is more established all the way up to secondary graduation. You may want to look up their IB results as well. ICA is relatively new, again, only hear great response from parents. Sounds like a promising school.
Here's what you were asking for (only comparing the kindie section in accordance to your question):
i) teaching quality, academic competence
- probably Victoria, since kids also graduates to local schools which has higher academic requirements (not necessarily a good thing, depending on one's view on what early education should emphasize )
- SWCK has more caring loving teachers
ii) English/Putonghua learning environment,
- Victoria is trilingual at entry level (for the local canto kids), then slowly streamline into English/PTH
- Again, Victoria should have better Chinese
iii) teacher to student ratio
- Not sure, but i am sure you can find out from the school (either their website or call 'em up, don't be lazy now!)
iv) the chance to get in International schools?
- SWCK, unless you are considering the local Internationals like ISF... oops, ISF is technically not an IS.
- please specify which type, best if you can list some target schools. Victoria has a list of where their kids graduates to (at least the time time i look onto their web 1-2 years ago), you can also do the same for SWCK - just ask the school, they probably has the most accurate answer.
Hope this helps