Actually, neither one of the cameras you mentioned is an SLR. SLR stands for Single-Lens Reflex, and typically refers to still image cameras that have interchangeable lenses. The acronym for the modern digital iteration of the SLR that also shoots video is DSLR.
That said, of the two cameras that you mentioned, I would go with the JVC, as it shoots progressive video. The Sony only lists interlaced video in its specifications.
However, if you really want quality footage, go for an actual DSLR, like a Canon EOS 70D. It has a larger APS-C type sensor than the other cameras that you mentioned, and it will give you a very nice image.
Personally, I would go for a MILC (Mirrorless Interchangeable Lens Camera) like the Panasonic DMC-GH4. Although it only has a Micro 4/3 sensor, Panasonic has made it clear that this camera is designed for high-end video production, with the available docking base that also has audio inputs, as well as the fact that it shoots 4K video footage. I own a GH2, and it has become my favorite camera in my arsenal. The GH4 is 2 generations newer than my GH2, but Panasonic has only made improvements on this line of cameras. Check the reviews on the GH4.
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