There really are a few. The X-Terra 70/705 can operate at three different Freq's, 3, 7.5 & 18.75, but you must change the coil for each one, keep in mind that the 705 comes with the 7.5 stock coil only, the others must be bought separately.. The EQ 800 operate's at 5, 10, 15, 20 & 40, all at the same time without changing the coil, and you can also use just one Freq. by it self if you choose to by (as Hal2K) said by pressing a button. The EQ's can do everything the 705 can plus more, in every category, in addition the EQ's are waterproof whereas the 705 is not. Dollar for dollar, between the 705 and the EQ 600, you really would get the most bang for the buck with the 600, no contest really, if you can spend a little more, then I think the 800 would be all the detector you would ever need for just about any type of hunting. Make no mistake, the X-Terra was a great machine when they were introduced, and you know they still are, but minilab has advanced it to do better today with the EQ series. For me, and speaking only for myself, the 800 has rolled the X-Terra 70, the AT Pro, and the Safari into one machine.