If you get into the world's top 10, how much you make basically depends on your ability, NOT the school name anymore.
I think that INSEAD is the better school. The alumni network is one of the largest in the world, comparable to HBS and Wharton. The location is 100 times better than London. If you have lived in London for more than a few months, you will know how depressing that place can get.
ARE YOU kidding? do you know how many job opportunities that offer great pay in London compared with Paris? London is the financial (as well as great law firm, accounting/consulting firm) centre for the whole EMEA, esp. IB, HF, PE/VC jobs. Paris can only provide less than 10% such finance opportunities compared with London, needless to mention that Insead is in the suburb of Paris.
Even more INSEAD MBA work in London than Paris. Do you still think Paris is a better city?
No, I am not kidding. Let's not confuse job location with school location. Where you land your job is a totally different issue from where your school is. e.g. Most HBS grads don't work in Boston; Most Wharton grads don't work in Pen..
Futhermore, Fontainebleau is 40KM from the center of Paris, and is one of the most beautiful towns in France. I personally believe it's a great place to spend a year.
If you have statistics on job offers for both schools, please share with us. The numbers I have seen indicate that INSEAD is on par with LBS on job offers. Admittedly, LBS is stronger in finance. INSEAD is more towards MC, etc.