I have just started scanning with the LS-8000 so it is difficult to give a complete answer but I paid about $1,200 for mine which about double than the V700. So for me it is a no brainer to get double the resolution for double the price...
That said the LS-9000 goes for twice the LS-8000 which does not make much sense to me.

I have not printed yet but that is where you should see the difference between the LS-8000 and the V700. If you are looking at web and/or small prints then the choice is not that obvious.

Cheers,

Luc