Of course they do perform better at etreme altitudes, and they are easier to maintain. Sort of an AR vs AK question.
But the real question is why are we buying them ANYTHING? Afghanistan will not even pretend to be a nation state friendly to us 15 minutes after we leave. Karzia already stands against us. The Taliban is already poised to take power, and is even given legitimacy by us and Karzai.
Does anyone in their right mind think the Afghan army, will use these, to attack the Taliban after we leave?
This and the planned Super Tucano buy is a disgraceful fraud, designed to enrichen contractors and procurement officers. Anything else is an outright lie.
The Russian helos are also simpler to operate than Western ones.