It's a "Ford/Chevy" question. There's too many variables. There's no one "best", because even in the conditions you give, there is room for opinion on the degrees to which you're talking about:
Ie.: "fairly trashy" can mean one amount of "trash" to one person, and another amount of "trash" to another person.
"Deeper" to one person may mean 6 or 7". To another person it'd be over 8", etc..
And are you willing to get a little more depth on silver/copper, if it means the machine doesn't excell as well in low conductor targets?
In general, for park turf, at least in CA right now, it seems that Explorers are bringing in the deepies. But you're talking an expensive machine that ...... if you're a beginner ..... may just give you headaches and ear-aches that you'll hate.
So your question is really one where you may just have to try several different types, talk to proficient hunters in your area, and decide what works best for you.