I'd go with the A6.

I have an A5 Sport and am satisfied with it, but for a few bucks
more, why not get the latest whiz-bang features? Nothing is
ever cheap about aviation.

One thing others have not mentioned about the A5: it was designed
for use with a battery pack that outputs a higher voltage than is
obtained by using six AA's in the Sport pack. This means that even
when using fully-charged NiMH cells or brand-new alkalines, the low
battery indicator is always on. Does this cut down on the range?
I don't know. I have contacted Icom about this and they confirm that
there's nothing unusual about my radio. That's just how it is when
using AA cells, standard alkaline or recharable.

As others have noted, the nav features are useless when all you have
is a rubber ducky antenna. However, not all handhelds are equal. I
was amazed to find that, though a Yaesu could not detect an VOR until
I could hit it by throwing the silly little thing at it, a Sporty's
worked almost as well as the panel-mount. I did have an Icom along
for this experiment, but it was a COM-only so it could not play in
the NAV section. Tests were done with rubber duckies on the radio
and with one taped horizontally along the top of the windshield.

For COM performance, my tests were not sensitive enough to find any
difference.

And to the rental company, I'm really sorry about the duct tape residiue
on the window. I did try to get it off, but someone was waiting for
the airplane.