I haven't used the D2, but have read many comments on it in this and other forums. Some claim considerable more depth over the 6X10 and others say not that much. One poster that has a lot of experience said the difference wasn't enough to buy one if you already have the 6X10 and also mentioned the open coil design as being a pain when used in heavy grass or brush areas. I use the 6X10 for the majority of my hunting with the MXT and IMHO it is the best ALL AROUND general purpose coil currently available. However, my motto is "If you like it, use it" so I don't really have an axe to grind with those that don't agree and think the D2 is the cat's meow.
Dig often, dig deep,
BB