I'll give you my two cents worth on audio recorders as I have no experience with video recorders in qualitative studies.
If its a one off study with a small sample- it would be cheaper to use a mobile phone/tablet or similar if its in a quiet setting.
However if you are going to be continuously conducting qualitative studies and doing audio recordings it would be wise to invest in a dedicated digital recorder such as Sony or Olympus- they don't cost too much. I have experience with both brands of recorders and they do a great job of isolating the interviewer's and participant's voices especially with the external mic which is supplied with the recorder. I was involved in one particular interview which was done next door to a very loud party, but the recorder picked up the interviewer's and participant's voices only, and the recording was very clear.
When purchasing a voice recorder it is important to check if you need to import the digital recordings using the company's own proprietary software- which can be very annoying when operating systems are upgraded but not the software.
For example I have a Sony recorder whose software for retrieving the voice recordings can only be done on a 32bit Windows XP computer. So be careful when purchasing a recorder.