I believe they are both effective at cleansing the liver, which is of greatest importance. When dealing with cancer, most people use their sauna solely for the liver cleansing effect, which in turn works to combat the cancer.
If you are after direct therapy of a tumor that is close to the skin, then the lamp sauna would be preferable, as it reaches a bit deeper into the tissue. The benefit to the liver, however, is not dependent on the depth of the rays reaching into your body, but rather as a result of the intense sweating.
The far-infrared sauna is easily avaiable to purchase online, but the wooden models can be pricey. There are inexpensive soft-sided portable saunas for a few hundred dollars. I purchased my sauna from National Pool Wholesalers.com I have a wooden sit-down model that has a hole for my head to stick out. I just love it! However, the last time I checked, they were n't carrying that model any longer. It was reasonably priced, also, at about $600.
The near-infrared light saunas can be built at home fairly easily and cheaply if you prefer. Dr. Wilson offers simple plans here.
As for the length of time to sauna, the recommendations vary widely. On the radical end of sauna therapy, where the sauna is used as the major part of healing, it is used for an hour, two or three times a day. This comes with its own set of precautions as to the electrolyte imbalance possible from all the sweating. If you want to use it this much, you should do some further research about using it to that extent.
On the modest end of the sauna therapy spectrum, it is said that 15 or 20 minutes a day will do, just so you work up a good sweat to get the toxins out. That's the sauna philosophy that I subscribe to, as it is obviously easier, and, since it is a supplement to other parts of my protocol, not the mainstay of it, I believe my 20 minutes daily to be adequate. People with many tumors would probably benefit from longer, more frequent sauna sessions.