Hey
mbapenguin ,
I was also in a similar situation as you a couple of months ago - I was hesitating between Oxford/Cambridge/IESE/LBS.
Below are my thoughts based on what I discussed with alumni:
Quality of education: If by quality you mean the content of the programmes and what you will learn, I think the quality of the programmes in top schools is the same as I have heard several times that the content is pretty much the same. Some schools might put a bigger emphasis on some topics (for example they have a research center in healthcare or an emphasis on climate change in the programme) but from my research these schools will often invest in similar topics. The differences are in the details - Cambridge has 3 projects and I believe INSEAD has 1. INSEAD has more electives and they are different than the ones of Cambridge.
Entrepreneurship: My goal is also entrepreneurship and I think both schools will get you great opportunities. The main difference I found between a big uni vs a pure business school is that your network will be different - the first will give you more opportunities to network with people outside the business sphere and you will be exposed to research on various topics outside of the business field. A pure business school gets you a stronger and larger network in business fields.
Traditionally, everyone will tell you INSEAD is focused on consulting and Cambridge on entrepreneurship but you will get cool startup opportunities (competitions, courses, etc.) in both.
Personally out of the schools I applied to, I think Cambridge had more students interested in entrepreneurship, but this is based on a small sample of people I talked to.
Network: From my view, the network is indeed important. When you will need help on your project or want to sell your idea to others the first people you will contact apart from your close network are people in your school's network. Similarly to my previous point, I think both can get you many benefits and the key difference is what kind of network do you want to have (mainly business or a wider one). To be clear, you can also build a network by working hard and most people do that

If you want DM me and we can talk more in detail.
I still suggest you reach out to current students and alumni because I haven't gone through the programme yet.