Doing same evaluation
I am also considering the same two brands for our 460. I beleieve either will withstand the conditions if you get a sunbrella cover for the wheel and fibreglass mounting structure when the boat is not in use. I might also remove the unit during winter layup. I'm leaning toward the Garmin since the new Blue Chips for the newest units are far cheaper than G Chips or the Chips used by Raymarine. For example, the entire Chesapeake bay can be covered for $300 with Blue Chips and its over $1000 for the chips used by Raymarine. On the other hand, he advantage of the Raymarine is compatability with the Autopilot but the Garmin can send waypoint steering data to the Autopilot. If you plan to add radar, also consider the monochrome or color Raymarine Units that can display Radar or navigation data or both. They can also be set to display radar and nav data in the same format so you can quickly tell if a target is a lighthouse or mark or some other non fixed target.
