The question seems to be not "Is Ada better than C++" but "Will Ada be around
in 10 years time."
Other posters have answered the first question well enough. The Slides on http://www.adaic.org/docs/present/whyada/
give hard numbers, facts rather than opinions that make a strong case.
But history is replete with technically superior systems that have fallen by
the wayside. The classic example is VHS vs Betamax. But even there, it's notable
that professional studios, TV stations use Betamax, it's still around when quality
The best argument to show that Ada will still be around -or will not be - is
the number and variety of systems in use, and any figures to show that the market
is growing rather than shrinking.
<insert URL of lists of users, including Reuters, Boeing, TGV, Channel Tunnel,
Air Traffic Control systems etc here>
In addition to which, we must add that VHDL is basically Ada. And that has become
the standard tool for hardware design. This means that Ada will be as hard to
kill as a cockroach, harder even than COBOL.