My thoughts are that the c24s are more comfortable and feel better through corners than the a23.

The braking surface on a23 is of inferior quality and performance, and it is very narrow too. The rims I think are pretty low quality.

Personally I think you'd be wasting your time building the a23 rims as anything other than a super budget wheel.

As for the c35s, well I don't know about the clinchers but the tubs are stunningly good. Stiff but smooth as you like.