Sushmita, I had admitted my daughter this year for nursery session starting 2018-19. My son is going to a different school. Probably someone else can help you better. 

My points behind opting it are :- 

1.) Distance of school is just 2 km from my home while the other are around 4-6 kms. Shorter commute time will atleast take away the travelling stress providing more time to play for my little one. 

2.) Academics wise my personal opinion is that all the schools are more or less same. I am very much satisfied with my son's school barring a few points for which I feel I should taken better care of rather than expecting much from school. 

3.) People talk a lot about ECA. ECA is good in one way like my son is not having any stage fear but a lot of it like the case in Apeejay/Amity/DPS could be a pain with you may need to run around the dress rental shops at last moment notice. Apart from that I do believe that Somerville must be having stage activities like drama etc. in a balanced way. 

4.) In my personal opinion Sports is having a backseat in every school. Basically what happens is that you cannot expect school to teach a class of 30 - 40 people teaching tennis or any other sport to your kid in a matter of 30 mins class once per week. So generally what happens is that kids whose parents are taking them to sports classes (externally) generally perform well and got the place in school teams for the inter school competitions. So this is one point you have to put in effort to explore out the potential in your kid. And yes what goes for Sports goes for music and other activities too. So I will not chose any school considering this parameter. 

5.) People say kids get a lot of homework in Somerville, well I think with practice kids retain the things more and it's good. With wife putting in all her effort with kids I believe this should not be difficult. 

6.) Reputation takes a beat and I will say SN is much more reputed as you can see in this forum and elsewhere. So going with public opinion do makes sense. 

7.) Toughest but least priority point for me was having siblings in different schools. But I think on a positive note it will help us to see the difference and probably if we need to make a switch after some years we will have much better clarity on what to do.