I'm a low budget film maker.
Both cameras are around 1000$~ and have similiar features and specifications.
The importance is: Video quality, convinient manual controls (W.B, Aperture, Focus) and robust (Though compact) construction.
External microphone is a must.
I really have hard time to decide between both. I have read that the GS-500 is not as good as the GS-400 and there aren't any real in depth reviewes about the JVC GR-X5US (that looks very promissing IMO).
What do you think? Please assist.

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