On Wed, 12 Dec 2007 10:28:52 -0800 (PST), Paul kgyy
wrote:

Looking over ads for used aircraft, I occasionally see a combination
of a Garmin 430 GPS with a MX-20 mfd.

What does the MX-20 display provide (other than size) that you don't
get with the Garmin 430?

Visual depiction of airways, sectionals as background, SafeTaxi, Jepp
ChartView/Garmin FliteCharts. It can also control stormscopes, radar,
EGPWS, etc.