You really should go for the 495 (don't bother with 496) for the following reasons:
1) it updates the GPS signal 5 times per second which makes the turn co-ordinator on the panel page perfectly useable in an emergency (such as horizon failure in IMC)
2) It has Visual Reporting Points in the database. Absolutely essential if you haven't been able to pre-plan with Bottlang or whatever (I had to divert into Elstree a while back and was told to report at the "golf course" - of course when you look around in that area all you can see are frigging golf courses !! )With the 495 just hit the 'Nearest' button and then go direct to the VRP which will be listed at the top (or near top)
3) The 495/6 have 'Obstacles' in the database. Again, a brilliant feature well worth the money.
Drambuster