If you aim at International schools ( with Vicotira counted as one), then go for Victoria. However, please note that only around 16% of all Victoria Kindergarten graduates can get admitted to their primary. There is also news (or rumour) that they will implement debenture system (five hundred thound - though unconfirmed yet) for their primary students later.
Now back to St Catherine's, It IS a good school. Very systematic. Less homework that Kentville and they have done very well in helping their students to prepare for the interviews for prestigious primary schools. The only drawback is that it is NOT a through-train school like Victoria.
By the way, which one is nearer to your home? I would NOT recommend a school that's too far away from your home as it is very tiring for young kids to travel a long way, not to mention there may be many extra-curricular activities and much homework waiting for them when they return home!