Polak, the Ludlum device you are using will work fine for any dose that represents a significant hazard. It is designed to be a "get-out-of-dodge" device that doesn't require any more training than, "if it goes off, leave the scene". It is adequate for that purpose. It will not go off for a typical x-ray because the beam isn't on long enough to activate the detector. Find a fluoroscope or some radioactive material and it will work just fine.
The other devices you listed, although I am not personally familiar with them, are a little more advanced, and probably work just fine. The are designed for a different purpose though, and cost more money. They also require a little knowledge to know what info is being relayed to the user and what that information means as far as risk is concerned. As evidenced from some of the posts here, many first responders have not received that level of training.
Personal dosimeters (as mentioned in a separate post) have no alarming capability and are simply used to track occupational dose after the fact. I wear one everyday. They work very well, but provide no warning as to the dose or dose rate as it is actually accumulated, and are therefore not particularly useful for first responders.
We have evaluated several electronic personal dosimeters, and as far as simplicity is concerned the Laurus RADOS Rad-60 is relatively inexpensive and easy to use. They are fairly durable to boot. As you noted, there are lots of options out there these days, and if you don't know what you need or how they work you can spend a lot of money on hype, or buying more than what you need.
Any of these units will have to be maintained and calibrated annually to ensure functionality. This too costs money.
If you have any more questions on rad detection instrumentation, or rad safety in general, feel free to drop me a line (gsackett1 at hotmail dot com).
Be safe out there...
Greg