Is there any information out there that would indicate which is
> safer/healthier to use ... a 2.4Ghz or 5.8Ghz cordless phone?
> I'm not trying to get into a discussion of whether cordless phones
> actually pose a real health hazard, however, I would like to know
> which of the two is considered less harmful ... 2.4Ghz or 5.8Ghz > radio waves.
We all want simple answers to complicated issues.
Harmful to what in what way?
There are a LOT of variables in play. Older phones tend to have higher power levels as newer phones many times (but not always) have better DSP circuits and can pull out clear voice from weaker signals. Plus is it analog, digital, spread spectrum digital, etc ... All of this matters.
Are you worried about brain cancer, skin cancer, or something else?
To be honest I doubt you can come up with a clear choice just based on frequency and nothing else. It would be very dependent on make, model, production run, etc ...
For me, I'd buy 5.8 as that is less likely to interfere with wireless computer setups and other things you might own or buy in the future. :)