can I chip in here if I may
we have the JVC X7 & Sony VW90ES on demonstration, for me both are very similar with 2d performance, both being excellent and not much to call between the two. Probably the JVC has better black levels.
The Sony is without doubt imho the better one in 3D with fast motion handling, much smoother as Nick says, but I do find it initially to be less bright as the JVC whilst in 3D mode but your eyes adjust to it after a few minutes and then its fine.
One thing though that I think is important, I think the JVC`s 3D`s glasses to more comfortable to wear especially if you already wear glasses for everyday use.
Both excellent machines though with the Sony edging it on price