Welcome mate.
For some reason, a 4th Gen and a 5th Gen in the same relative condition (cosmetics, mileage etc.) do tend to run around the same price bracket. Personally I'd always go for the 4th Gen, I prefer the styling, but there's nothing wrong with 5th Gens.
Weight is hard to nail down, but 238kg with water, oil and no fuel is probably about right for the 4th Gen. I think that's what the manual states. The reality is that you'd be hard pressed to pick a difference between any VFR from 1990 to current, and the bike hides its weight quite well, especially once rolling. 5th Gen may feel a little more nimble to turn as it has a slightly shorter wheelbase (the side-mount rads were used specifically to allow the wheelbase to be reduced), and 6th Gen definitely handles better than all the earlier ones due to 43mm forks (earlier ones had 41mm forks).
Happy hunting.