Camtasia, Screenflow, or "Other?"
Both Camtasia Studio and Screenflow are full-featued screencasting solutions. Both allow you to capture, edit, and distribute screencasts. In the US at least, they cost the same (though Camtasia has a $99 "introductory price," I would be surprised if they raise it to the $149 "list price" as long as Screenflow is priced at $99).

Both programs have extensive editing capabilities, and will handle the kind of edit tasks you describe.

One (minor, in my opinion) difference is that Camtasia allows you to capture part of the screen, while Screenflow always captures the whole screen. But it's easy to crop to part of the screen in Screenflow during the post-recording edit.

It boils down to which program's interface and workflow you prefer. Both have free trial versions; I suggest you download both and produce a sample video in each. Then buy the one that feels right for your working style.