I'm pretty satisfied with Record, it has loud, clear playback on speaker (a tried a few others, but they were difficult to hear in noisier places unless I listened to them on headphones), and the ability to email a recording.
Enter 'Voice Recorder' in search iTunes, and you'll get a longer list of voice recorders.
I'm not betting on Apple's voice recorder, most of their other apps are outdone by other third party apps by a wide margin.