Initially I picked Insure and Go as they were the cheapest AND had the type of cover I required. A lot of them have altered what they cover in terms of natural disasters. We were in Lombok when the earthquake hit last year, also the week later in Bali. We were not affected but a lot of people with and without insurance were. Mostly now I make use of the free travel insurance offered by my bank's credit card, which seemingly offers the same as Insure and Go and any other companies I have researched. I do not have any pre-existing ailments with the exception of high blood pressure (this doesn't seem to worry any of them and does not increase my cost). Luckily I have NEVER had to make a claim. For my husband and I the most important cover is for medical and associated expenses. The rest is all replaceable, although you may be inconvenienced at the time.
An insurance policy for anything is only as good as what the company is prepared to pay. Unfortunately when it comes to the crunch some companies won't pay when their interpretation is different to yours.