I think you'll find that every person with different bikes in every zip code in every state will have different results. I shop every year, as rates seem to change - compared to with car insurance where I have only had two different companies since 1985. As an example, for me Foremost is horribly expensive for the same or less coverage than others. Since I have several street bikes, I also find that for a specific bike one company may be far more competitive for the same coverage than another - however for my 2nd bike it may be the opposite. It's like a massive conspiracy. Also, where one company may be the most competitive at a certain liability/comp level, when you change those policy levels another company may end up being more competitive. Here in PA it used to be better, until the anti-helmet idiots got the law changed making helmets optional. The (good) company I had at that time immediately stopped insuring bikes in PA. My company raised their rates this year and my Blackbird premium is too friggin high, so I'm going through the same search right now. I always check with (in no particular order):
Farmers
Dairyland
Nationwide
GEICO
ForeMost (though they have yet to have a single competitive quote in the last 8 yrs)
Progressive
Here at least, Nationwide and Progressive seem to "usually" do the best. But that is "my" zip code, credit rating, bikes, etc. Good luck. Insurance is the worst part of bike riding.