For me - as far as depth is concerned, high conductive coins (copper, silver, clad), Park 1 a bit deeper. Nickels, gold, lead, brass, smaller targets regardless of conductivity) and other mid-conductive relics, Park 2 is a tad deeper. Hard to say what the relative difference is but I have found deep silver with Park 2/Field 2 and have found deep nickels in Park 1.
When someone asks "which mode is better" best to specify the target type of interest because one can easily answer, "it depends" to the basic question. Way too many variables involved (target type, ground conditions, trash and iron density) all factor into the answer.
So, in general, if I am relic hunting, I like Field 2 or Park 2. In highly mineralized soil or thick iron, I sometimes use gold mode.
Park 1 for casual coin shooting.