It’s an aesthetic but I really like the DOF control with 1/2″ chip. It all depends how important that is to you.
You mention workflow. I’ve been using SDHC in my EX1 since January if that was a concern for you.
I can import the MP4 into FCP using CalibratedSoftware’s MP4 import plugin ($80).
I am concerned (although can’t confirm) how the JVC handles overcrank. Sony at 720p24/60 is recording at about 87.5mbps on to SxS. Apparently JVC is not recording at that data rate so they must be doing “tricks’ in their overcranking. Also the JVC only overcranks to double the frame rate. One way to do a comparative test though is to record at 720p24/48 or 720p30/60 on both cameras and note how quickly it fills a 16GB or 32GB card. Someone (not I) did this test and apparently verified the JVC is recording at a lower data rate which must mean either those clips aren’t playing back at approx. 35mbps or there’s some kind of interpolation going on.
Also the EX can do interval (time laps) recording whereas the JVC HM can not.
That said, there’s certainly lots of nice things about the JVC including the form factor but I thought you should take measure of the above.
Given the above I’d still chose the EX over the HM but I certainly wouldn’t fault anyone going the other way. I like 1/2 chips. I like the low light capability that brings as well and I like interval recording and the slightly better overcrank features.