I remember reading in an old paper festool catalog, that the C handle drills were more meant for precision drilling, (easier to put put pressure inline with the bit) and the T handle drills were for heavier tasks. (I can't check the exact wording anymore because I threw them away a few years ago; it was an older catalog with the predecessor of the original C12 drill, CCD or something)
I followed that logic and got the C12 li ion when they came out (before the introduction of the CXS) to complement my protool 18V (T handle). And I use makita impactdrivers for most driving tasks.