Thanks
Choose one of them
ISL has a "full" IB programme (PYP, MYP and DP). I say "full" because I don't think it does the Certificates but it probably has no need to and all students take the full diploma at 16.
La Cote is based upon the English National Curriculum, does PYP, MYP, IGCSEs (I would ask how they combine MYP and IGCSEs and why) and DP.
Academics should be fine in both but, as La Cote is considerably newer, ISL will have more experience dealing with different types of situations, particularly at the senior school level. On the other hand, La Cote is part of Nord Anglia, so can call upon the expertise of the parent organisation when needed. Neither should be a cause for concern. The only area they could differ is in expertise in uni applications and the number of subjects they offer, but will it really make a difference if your children are young? At the pre-IB level, I would think both are equally as good, but you would need to look at their results to see.
Look at their pastoral offerings and co-curricular programmes. This is where schools can differ. Generally, the larger the student body, the larger the number of activities and sports offered. Generally, but not always.
Look at the number of students in the school (the student roll not the capacity). Some children prefer smaller schools so that they know everybody and some prefer larger schools so that there is more interaction with different students.
If you really wanted to go to town, ask the school about attrition rates, particularly at the senior end of the school. If children regularly leave the school to go to other ones in the surrounding area, it should ring alarm bells.
Ultimately, if your children are young enough and you are staying long term in Switzerland, I would send them to a local school. It is really the best way of learning French and integrating.