Joe mentioned a smoother threshold, something else we've noticed from machine to machine. Some seem to run a bit smoother then others. The Excal I had before the one I own now wasn't as stable, the threshold just wasn't as consistently smooth in PP, really sensitive to water and wave action, always wavering a lot. The machine I have now is very smooth in the water, even when I put a good 12 x 15 on it. The machine I had before would run the larger coils ok in the water but only after adjusting the sensitivity way down. Sounds crazy, I know, but they just don't all perform quite the same.
PP or Disc? Depends on my mood and the conditions. For me, PP = intense hunting, really have to pay attention to every little change up, be in the right frame of mind for it. If I'm water hunting and there's a lot of current and wave action or the bottom is really uneven just too many distractions/disruptions since I'm going to be unstable on foot myself, so I hunt in disc mode. Same if I just want to cover as much beach as possible or when I'm not in that slower mood. But when the conditions and my mood are right I'll PP hunt quite a bit. I will say this, since adding the remote PP I do use PP a lot more often then I use to, regardless what mood I'm in as it has become a very convenient tool to access.