An image is quicker because you don't have to listen to the audio in realtime.

Total recorder also has a feature where you don't have to listen to it in real time. Streams to disk as fast as the application can send it. Whether or not this actually works depends on the player application, but it has worked in some of the cases I've tried it in. If you've ever seen WinAmp use its Disk Writer plug in to convert an MP3 to a WAV at a rate faster than realtime, then you'll know the kind of thing I'm talking about.