I would go for the larger screen device every time, subject to it being satisfactory in the other departments.
G496 has a much longer battery life than the Avmap whose battery life is ~ 1hr.
The Avmap has a much bigger display.
The Avmap is better for leg mounting; the G496 is better for sticking on top of the panel.
The G496 has a very good TAWS function which really does work. The Avmap claims to have TAWS but how good is it? The Garmin topo data is from space radar imagery and very accurate.
The Garmin has a flimsy power cable which many users have broken, often damaging the connector in the GPS.