Ring Flash (LED or tube light flash)

I am not sure which is best from LED or tube light. However, I use a sigma ring flash with no problems so there are alternatives to Pentax - when I was looking for a ringflash the sigma was certainly much cheaper than the Pentax. I cannot compare the quality of the two, however, as I have not used the Pentax one. One thing I would say is that the Sigma has two 'semi-circles' of light rather than a 'true' ring. Not sure about the Pentax one.

That said, I also find you can get decent results with a standard flashgun, with the power wound down, on a short remote cable held close to the end of the lens, or triggered wirelessly from the onboard flash. I know some people even get fantastically good results using a modified pringles tube or loo-roll to channel the light from the onboard flash, so there are all sorts of options for macro flash.

Not sure whether that is helpful or not

Regards

LED lighting has very limited range - but it is continuous lighting which helps with focus and composition

Do be aware that the quality of white LEDs varies greatly and so different makes will give different intensities, white balance, and light quality.

I'd combine the two
Use LED ring lighting to help and a wired flash to give some extra light and 3D quality to the light
Matt

I have used an inexpensive (less than $70 US) LED ring light to do macro work. It has worked well when I shoot my K-5 on a tripod at ISO 1600 stopped down to f8-f11. A quick pass through Lightroom and its denoiser yields excellent IQ at that ISO.