It is very difficult to get admission to either one. Your child is very smart. Only looking at the school fee, it make a big difference between the 2 mentioned schools.
My child got offer from both TSL and TT (International stream) too. After conducting research (consulting my child's KG teachers, parents of kids who study in each school, friends who are teachers in other schools, P1 placement records of my child's KG in previous years, secondary school placement records of TSL and TT), we have decided to drop off TT and vote for TSL. It is possible that we will neither choose TSL nor TT at the end, but if we only have these two, we will choose TSL.