In all honesty, how good your insurance is doesn't show until you need it.
From what I've seen, most all plans are about the same price. ($175-$200 for 1 year/$1,000,000 in coverage). Of the three places I know to get coverage, all of them require you to 'join' something at one level or another to get that rate.
So, in all honesty, I'd look at the actual carriers themselves. Just ask who they are and then check them out online.
I use the carrier that ADJA has though I used the carrier with WeDJ at one point. In all honesty, I didn't see a difference, but I also never had a claim. If I had a claim, I suspect I may have seen the difference quite quickly. And to be completely fair, NAME also offers insurance, but I'm not a member, and haven't used their insurance plan.
On a side note, part of the reason I used ADJA's carrier was that I was able to get coverage for my equipment inexpensively. It covers the equipment if it gets lost or stolen. The other reason why is that I can grab 3rd party certificates online and print them in a matter of minutes.