I have to say I have never found one detector with a stock coil that will do everything in every environment. Multi-frequency, single frequency VLF, pulse detectors, each is unique and will produce better results than others in specific environments. Add in coil size 4" to 18" or larger the physical size and area covered one has to choose which will find what one is mainly looking for. Waterproof, water resistant 10' or 200' or land use only. Audio speaker or headphones; wired, Bluetooth, proprietary. Analog discrimination or notch filtering? More choices and they are yours to make. Myself, I have 17 detectors and countless coils and I believe I can pick the best for the situation I will will be detecting in for a specific item. Some challenging areas: in a house attic, heavy and over grown brush, trashy areas with a specific item to search for.
Just like good golfer, mechanic or dentist, a detectorist really needs more than just one "tool" to obtain the best possible results.