...why would I NOT get a 480 vs a 430W ?
I've got the Comanche search narrowed down, and there will be a panel upgrade, so for "only" 1500 more, what's the down side to the 480?
Ed, I think the biggest consideration is whether or not you will be adding a MFD (GMX200 or EX500) and/or terrain, XM-Wx, or active traffic in the not too distant future. Without a MFD the GNS480 is pretty limited WRT what can be displayed on the screen. There's no way to put XM or terrain on it and the only options for traffic are TIS (Garmin 330/33 xpndr) or Skywatch. In addition the 480 lacks the E6B and programmable VNAV functions found in most GPS navigators including the 430. About the only other downside to the 480 is that since there are many more 430/530s installed you are much more likely to find the latter in a rental or CFI client's airplane making your experience behind the 430 more valuable in that regard.
But the 480's list of advantages is significant:
30% larger map with more detail.
Airways on the map
Airway routing (more on this below)
50 stored flight plans vs 10
Stores multiple FPs between the same two airports
Roll steering for nearly all segments of any approach*
Programmable hold at any waypoint
Roll steering during hold entry
Roll steering during holding turns and both legs
Recall of last 10 Com and Vor frequencies used
Save and recall (with names) of frequently use freq's
NOAA wx receiver
Remote control of Garmin xpndrs
Auto Standby/Alt control of Garmin xpndrs
Configurable data fields for three Map plus HSI pages
Separately selected range for four map displays
Eight Direct options
Runway pointer during approach
Alternate airport selection
Display of radial/bearing/ID/Distance for any VOR on map
Heading numeric and graphical display
Automatic sequencing based on altitude during missed
Single button return to Map display
Audio callout at 500 AGL on approach
Displayed OBS course on map.
Monitor standby comm and vor frequency.
*note: Current software cannot provide guidance on heading based legs but the soon to be released version will do that. The 480 does provide guidance through any procedure turn as well as the entry and pattern to any hold.
WRT airways, the 480 provides three useful functions the obvious one being the display of airways on the maps. The less obvious functions are the ability to include all waypoints along an airway into a flight plan automatically (this is a BIG advantage if you fly airways) and the automatic prompting for the airway entry and exits available from any waypoint in a flight plan.
You will hear lots of folks say that the 480 is more difficult to learn than a 430/530 but that's mostly untrue. The truth is that there is more to learn on the 480 because it offers more (see list above). Also the user interface is different than that used by other Garmin products but it's very logical and relatively intuitive. One very nice aspect of this is that you can access virtually every feature by pushing buttons with the rotary knobs used only for selecting digits, characters, and items from lists and most items are located within two levels of the top menus.
Overall, I'd say that the 480 is better suited to IFR flying and users who like to extract the full benefits from any equipment they use whereas the 430 is more attractive to VFR flying and casual IFR use. That's not to say the 430 isn't adequate for significant IFR flying, just that the 480 is better. And IMO the biggest advantage the 430 has is it's terrain feature.
BTW, I was under the impression that the 430W was about price neutral with the 480 (the 430 non WAAS was less).
It would be sweet, but voice recognition software requires more improvement.