The AG-HPX370 represents a minor upgrade over the AG-HPX300, with the biggest improvement being the 1/3-inch CMOS sensors which should produce less noise and better sensitivity.
The GY-HM790 is also very similar to it's predecessor, the GY-HM700. new features include inproved studio capabilities a redesigned studio adapter, built-in time code in/out and genlock. JVC also announced a low light version, the GY-HM790LL, which will be released in the Autumn.
Both are outside of my price range (though interestingly, in broadcast these cameras are considered "low-cost!") I'm still waiting to see what Canon announces, and how it compares price and feature wise with the Sony XHR-NX5U.
- Broadcast & Cable: NAB 2010: Low-Cost Newsgathering Heats Up