I think you're all looking at this the wrong way: You have to look at what the company delivers to you in the very worse case scenario. Insurance isn't about lost luggage or delayed planes. Its about being seriously hurt or becoming seriously ill. When it happens all you want is the best care in the world. Or if you're in a 3rd world country all you want is out of there. So all this banter about 178 pounds or 200 pounds or 220 pounds. Get the best insurance underwritten by the best companies like Allianz or SITE.
Relative to total insured travellers very few people have nasty accidents or medical emergencies so its hard to find reliable data on this. In my line of work part of what I do is assist young travellers to communicate with insurance companies and family when they are seriously injured and unable to help themselves. In all cases of medical emergencies the insurance companies have provided excellent service. Their networks spread far and wide; you could speak to them 24/7; they dealt directly with the local doctors and medical staff and police and even booked flights home. The main issue that came up were people getting very upset when the insurance company wouldn't fly relatives to Australia to be with their injured sons or daughters - so check that one. In one case a girl with a broken shoulder was flown home business class, and so was her best friend.
Its at the other end of the incident level that most problems occur: lost luggage, stolen luggage, etc. It all depends on the cirumstances because what most people don't realise is that they themselves have a duty of care to look after their stuff. If the insurance company thinks they haven't excercised this they say "no way are we gonna pay."