I have a 496 and the Aera 550. The 496 is primary nav in our Rallye and it works exceedingly well. The Aera is better as it has the bigger, touch sensitive screen but it is essentially the same software and same mapping functions (which I am glad about). I got the 550 as the TAWS is higher resolutionthan the 500 (same as the 496) and also it has the capability to display traffic info on it, which I *believe* the 500 didn't. The 550 will be backup to a 430W.
Both great units, the 550 is much slimmer and can be mounted on a panel in a semi permanent fashion whereas the 496 has an odd shaped case and is too fat and needs to be sunk into the panel (CAA concerns there). The G696 is just too big to manhandle around the cockpit in my view, would be ok if it was panel mounted.