I had the chance to test the two planes today, side by side. Some comments, in no particular order of importance:
LV: well machined, but not finished to the level of the LN has a very well machined bed for the frog innovative adjustable mouth no slop detectable large grip
LN: very well machined and finished fixed mouth small (Stanley standard size) grip zero backlash
General. I would be very happy to own either plane, but would only buy and use one - the LV. First, I have large hands and the LN does not let me grip the handle unless my little and ring fingers are crossed over - awkward. Second, in use, my 'pointer' finger is in contact with the back of the blade. When I squeeze the handle to push the plane my finger digs into the blade parts (screws etc) - painful.
Value for money, the LV beats the LN hands down. After careful fettling of the LV, I'd be very surprised if the two didn't perform the same, with the LV being more flexible due to the adjustable mouth.
As a disclaimer, I own LN planes but no LV, yet. My viewpoint is as a user that likes very well made tools but insists on great useability coming with a high price. In my comment above, relating to the finish of the LV, it should in no way be taken to mean a lack of precision in the manufacture of the item. I am referring specifically to the 'cosmetic engineering' aspects i.e. plating, polishing, rounding edges etc. I am confident that the engineering tolerances would be very similar between both companies.
Greg