Coilfisher,
That was some sound advice, but I've got a feeling you are looking at this detector because you want to find small gold chains and other forms of jewelry, correct? Forgive me if I'm wrong and you can disregard everything below..
The Gold Bug Pro DP will do just fine on coins as long as they aren't deeper than about 6" (more or less depending on soil conditons).
But in researching this, I think the Gold Bug Pro with the standard 5" coil is probably a better bet for park hunting as it really helps to navigate the trash much better than the 11" will. If you want a bigger coil to go with it, the 5x10" elliptical coil seems to be the way to go. Users seem to much prefer it over the 11" coil and there are several YouTube posts that show it detects smaller gold deeper than the 11".
Now here is where I have to give you a word of warning. The GB/G2 line does an excellent job of knocking out iron, but these detectors absolutely love low conductivity targets like gold, aluminum, and tin. And bottlecaps. Good heavens they LOVE the bottlacaps. So if there is a lot of this trash in the ground, be prepared to do a lot of digging of very small bits of trash like can slaw, tin foil and the like. I must emphasize: A LOT OF IT! The very jumpy target ids most people discard as junk, but you probably won't get many of those. You will get some very solid VDI numbers.
This machines locks on to metal like nobody's business and you are going to need a good pair of knee pads as you will be on them a lot.
This detector will pick up on small and micro jewlery better than any machine on the market (yes, I know I'm throwing a gauntlet down here, sorry.
). But you are really going to have earn it by digging lots of junk.
I think this is part of the reason way it was made for nugget hunting and relic hunters like it so much (as there tends to be less junk in relic territory), but not necessarily emphasized so much for park applications. It's hard to cherrypick with this detector because bottlecaps will ring in as quarters, etc.
Having said all that, I have always been a firm believer that the detectorist who digs more finds more of the good stuff. And this detector will help you do just that. But you must have the right mind set otherwise you will get frustrated very quickly.
Did all that rambling help?