Unfortunately I haven’t seen any comprehensive comparison of the terms and conditions that different companies offer (which is a shame – hopefully someone will provide a link). However, the things that I came across personally:
Volcanoes and similar natural disasters – after the issues with Icelandic eruptions, many (reputable) companies refused to cover the resulting losses. So I would double check with the company whether they (a) cover these things (b) covered it last time it happened.
All sorts of sports and/or work – if you are planning to do sports or work double check that you are covered. Especially if its “extreme” sport (surprisingly wide category for the insurance companies) or involves any sort of competition. Wintersports cover is also usually included at a premium.
Cover for the USA and Canada can be more expensive than the rest of the world.
Not entirely sure if this is what you’re after, as it’s still a bit vague – but for adventurous travellers like myself, and others I’ve met in stranger countries regularly use WorldNomads.com.
It’s all purchasable and able to be edited/renews/claimed against online, which is great for travellers without say, a regular permanent address that some companies require you to have.
I’m actually getting a new policy with them tonight – albeit for a simple visit to Canada 🙂 (assuming no more riots!)
Credit:stackoverflow.com‘