Hi Christ,
I start with your Airstream question.
Airstream has nothing to do with the drill, it's about current Festool batteries and charger.
In short: Airstream batteries are designed in a way that air can travel between capsuled groups of cells. The Airstream charger is equipped with a fan that ensures air flow in these "tunnels", cooling them while charging. This is how Festool realized faster charging times without putting extra stress (heat) on the battery packs.
If you'd like to know how it works, take a look at this scene from [member=11196]Peter Parfitt[/member] 's video of the Festool Blogger Event in Germany:
=4m46s
And here you have [member=41214]Phil Beckley[/member] explaining it:
So whenever you come across SCA following the tool's name/set description it means that the tool/set comes with the Airstream charger. If you buy a tool/set without SCA in the name/description it will come with current Airstream batteries, but the non-Airstream charger TCL6 - plainly resulting in longer charging times. Of course, everything "Basic" - just as before - comes tool only without batteries or charger.
All of this is compatible with each other: You can charge Airstream batteries on both chargers, and you can charge non Airstream batteries on the Airstream charger (although, this will be as fast/as slow as before) Only Airstream batteries on a Airstream charger will benefit from each other.
--
As others have said, T vs. C or C vs. T

is purely personal.
I love my CXS and wouldn't want a TXS.
I love my PDC with T-Handle and wouldn't want a C style handle on it. (If Festool ever decided to offer that. PDC and DRC are T-Style only)
Kind regards,
Oliver