I have an Airmap 500 but have not had it that long.
I have used it on only a couple of flights and think the
display is easier to see than the 100 I had before.
Shade and darkness should be no problem with the back light on.
In direct sunlight the only problem is the light shining off
the face of the unit. The display is still very readable.
The font size is larger than my old 100 and the updates cost about $35
I think, maybe cheaper if you get a yearly subscription.
Some of the functions take a little geting use to but I think
that would happen changing from one model to another anyway.
I kept my Airmap 100 just incase but so far I like my 500.