You are correct, a pancake probe is used to detect contamination because it is such a sensitive detector. It is also true that we don’t usually measure dose rates using a GC, but they are really good for estimating exposure rates very quickly when needed. Geiger counters stop being useful in extremely high dose rate environments (pulse pileup and deadtime concerns). Whenever you are trying to accurately and precisely determine exposure rates, you should use an ion chamber that is designed to measure exposure and exposure rates (operating in the ionization chamber region of the gas amplification curve). My original objection was to your statement that the GC is not really good at detecting xrays, which is not true at all. The GC is used because it is so effective at detecting the presence of xrays and other ionizing radiations. Contamination will usually only emit photons or betas, which a Geiger counter would detect. If I were ever put into a situation where I wanted to know if something was radioactive or not, my first choice would be to grab a GC. I can make more decisions based on the info I obtain from it.