Back in the day when recording consisted of dragging a bunch of rust stuck in plastic past a magnet, punching was a very common technique to fix mistakes. When DAWs matured, it seems comping and working with bits of audio on multiple tracks became more common.
I had neglected punching until I was doing a project with someone who used Pro Tools, and he did a lot of punching (BTW he has since switched to Sonar and is much happier

). So I've been thinking about when to comp, when to punch, and when to combine the two...and I've come up with a workflow that seems viable. I offer this NOT as a "this is the way to do things," but rather, because others might find it helpful or have suggestions for improvements.
1. Start off with comping. However, if after recording a few takes I think I mostly have the part down, then as the comping continues I'll sing or play only in the parts that I think need improvement. This kind of combines the mentality of "punching" with comping, because I concentrate on a specific section that needs work, even during the comping process.
2. Edit with speed comping and create the part. If all is well, then I'm done. But...
3. If after listening back there are one or two things that bother me, I'll punch just those changes on the otherwise "finished" track.
This seems to be the most efficient way for me to work. But I'm always up for trying new ways to do things, so if anyone has comments on punching vs. comping, I'm all ears.