Maybe try to find some unbiased statistics about vet bills for dogs (excluding pedigree, which are often more likely to require treatment). That's essentially what you're weighting up: how likely is my dog to need expensive medical treatment (which would save its life and return it to health, rather than prolong life unnecessarily - I too am not in favour of extending an animal's life when that quality is not good enough)?
You then have to decide if you can afford to risk not having insurance. Chances are, you wouldn't need it, and the little incidental bills, while irritating, would not be impossible to meet.
It's the big bills which pose the problem, and only you can decide whether you could "afford" to meet them uninsured. Perhaps see what the cost of, say, a seriously broken leg, or commonly suffered trauma from being hit by a car, is for a dog of his/her size.
For instance, our dog (then a puppy) received about £4000 all-in of cutting-edge surgery and treatment after an accident. He was/is insured: I could never have met that bill, and would have had to have gone for the cheaper option (just a cast) without insurance, which probably would have left him with an uneven gait and lifelong problems with his leg.
Recently, he committed a "dietary indiscretion," which, had we realised even an hour later (we were out and came back just in time to whisk him to the emergency vet), would have meant the objects would have moved to his gut and he would have required surgery to remove them (as it was some Oramorph meant he puked them up, poor lamb). In that instance, I was relieved to be insured, not because I could recover partial costs for the couple of hundred for the emergency vet and the injection, but because I knew that, unpleasant as it may be, I could give the ok for surgery then-and-there, regardless, had it been necessary, rather than be forced to wait and see whether he would be one of the lucky dogs who poop out the objects (less likely, as he's a small dog).
Anyway, trouble is, for everyone who has a healthy, accident-free pet who lived to a happy old age, you'll get responses from people like me who couldn't have managed without their insurance. Only you know your circumstances well enough to decide. Good luck with your decision! 