I have the FL-18 with the Genz pack and absolutely love it. I would never buy a unit without the 6' bottom zoom.
I am not as familiar with the Vexilars.
Is the zoom on the Vexilars movable like it is on the Marcums?
Having the movable zoom is great when there are suspended fish like crappies. I can move up the zoom window anywhere in the water column to key in on the area the fish are in.