Here a 276C is 639 can dollars (679.934 AUD) and 550 Zumo is 919 (978.191 AUD).
I have a 276C and really like it. It does what I want.
The Zumo does had more non-GPS stuff.
"Add Optional Traffic, Weather, and Radio
With optional XM subscriptions and an XM antenna, you can check the weather, move ahead of traffic and listen to the radio when you travel with zumo. As an alternative, zumo can receive optional TMC traffic alerts (in select cities) when used with a compatible traffic receiver. Simply press a button on the screen, and zumo recalculates your route to avoid traffic tie-ups.
Make Hands-Free Calls and Receive Wireless Voice Prompts
With zumo’s Bluetooth® wireless technology, you can talk on the phone safely without removing your gloves or helmet. Connect zumo to your Bluetooth-enabled headset/helmet and cell phone to make and receive hands-free calls. You can even make phone calls to POIs through zumo’s Bluetooth interface. In addition, zumo transmits navigation voice prompts to your headset so you can listen wirelessly."
zumo 550 Features
• High-sensitivity GPS receiver
• Display: 2.8” W x 2.1” H (3.5” diag.), 320 x 240 pixels; high bright sunlight-readable, UV-resistant, touch screen display
• Unit dimensions: 4.8" W x 3.9" H x 1.6" D
• Weight: 10.6 ounces
• Removable lithium-ion battery; three hour typical use
• Bluetooth wireless technology for hands-free calling and navigation audio prompts
• Supports optional FM TMC traffic alerts
• Supports optional XM NavTraffic with XM weather, and XM Satellite Radio
• Preloaded maps for all of North America
• Voice announces streets by name
• Look up addresses and points of interest
• Choose 2D or 3D map perspective
• Upload custom POIs, including alerts for speed zones and safety cameras
• Built-in MP3 player and JPEG Picture Viewer
• SD card expansion makes it easy for storage and route sharing
• Export and review your travels in Google™ Earth with a free account from MotionBased.com
• Glove-friendly touch screen with left-handed controls makes it easy to operate
• Sunlight-readable, UV-resistant display makes it easy to view your screen
• Motorcycle console for trip information, including fuel gauge to warn you when it's time to fill up
• Motorcycle mount with standard 4-hole AMPS pattern so you can mount it anywhere
• Included motorcycle mount for riding and automotive mount (with integrated speaker) for driving
• Includes Garmin Lock™, an anti-theft feature
• Custom caps, available in a variety of colors, to reflect your style
• Waterproof: IEC 60529 IPX7 standards (submersible in one meter of water for up to 30 min.)
Package includes:
• zumo 550
• Preloaded City Navigator® NT North America
• MapSource® City Navigator NT DVD (full-unlock)
• Motorcycle mount with RAM mounting hardware
• Automotive suction cup mount with integrated speaker*
• Dashboard disk
• Carrying case
• AC charger
• Vehicle power cable
• Motorcycle power cable
• USB interface cable
• Security screwdriver
• Custom caps (silver and black)
• Garmin stickers
• Owner's manual on Disk
• Quick reference guide
But, I just wanted a GPS and one that I could use with batteries off the bike, so I got the 276C.
GPSMAP 276C Features
• 3.8-inch diagonal, 480 x 320 pixel, 256-color TFT screen with adjustable LED backlight
• Unit dimensions: 5.7"W x 3.2"H x 1.9"D
• Adjustable marine mounting bracket
• Stores up to 3,000 user waypoints, 50 reversible routes (300 waypoints per route)
• 10,000 point automatic track log; 15 saved tracks
• Area calculation feature calculates the area enclosed by a track
• Rechargeable lithium battery offering 5-15 hours of use (depending on backlight settings)
• WAAS-enabled, 12 parallel channel GPS receiver
• Adjustable quad helix receiving antenna with remote antenna capability
• Built-in basemap with automatic routing and turn-by-turn directions
• Accepts standard Garmin data cards for storage of downloaded MapSource data and pre-programmed data cards
• Provides separate serial and USB interfaces
• 2 NMEA serial ports
• Offers BlueChart night mode for easier viewing at nighttime
• Large numbers option for easy viewing
• Position formats include Lat/Lon, UTM, Loran TDs, Maidenhead, MGRS, User, and more
• Provides a course deviation indicator when navigating
• Project your position on the map with the configurable complex heading line
• Built-in tide tables and celestial tables for sun and moon calculations
• Alarms: anchor drag, arrival, off-course, proximity waypoint, and clock
• Water resistant to IEC 60529 IPX7 standards (submersible in one meter of water for 30 minutes)