I have worked in the City long enough. There are plenty of burned out and seriously unhappy 'world domineers' in there.
Remember that pastoral care covers far more than say, an incident of bullying. A bereavement, redundancy, illness in the family, divorce... How (or even) will the school support you? If your child lacks the Gengis Kahn instinct or is dyslexic, or has other secial needs... Will the school help or show you the door?
Have you the extra resources for the intense tutoring that you aren't supposed to admit to (that everyone really does) or trips 'of a lifetime' every half term?
What is the school culture like - is it a snob-fest of bragging rights, or are the parents down-to-earth types who you can imagine taking the kids to the park on a Saturday afternoon for ice cream. Or are they the types who get nanny to take them out for the whole day, or have the live in tutor to help them write an article to submit to the HBR? Can you be a**ed with people like that?
You know yourself and your child. You know your family, and what you aspire for your child.
Experience tells me to go for the pastoral care and good culture of the school every single time. A happy child will learn. An unhappy child will kick and scream and fight it - or worse, turn inward, knuckle down and possibly get ulcers by the time they hit GCSE.
Look very closely at the children at the school and the parents/nannies. If your radar goes off, then listen to it.