I have a simplex and I like it a lot. I almost got a vanquish 440 instead. My fried recently bought a 340 because I told him to get a vanquish just to see how it compares to mine. His VDI is much more consistent where my simplex gives off a wider range of VDI for the same target. His VDI buffer zone is like 5 and mine can be 20. We only look in trashy areas. Will buying a SP24 coil help me ring my VDI range in tighter or should I just buy the cheapest vanquish and have 2 detectors?