Ok, so perhaps this isn't a topic for a gear forum, but it's directly related to GPS units like the Prostart or Sailmon Max, in comparison to a magnetic compass like the prism or Tacktick. I'm in the market for new electronics but need to understand what I'm buying prior to picking a unit. I've been told by multiple Pro's that I trust that on my Star I really want a magnetic compass because it is way better for showing wind shifts. Several of the top Star boats, Paul Cayard and Robert Scheidt for instance use the Prostart on their boats which is GPS. The people that told me to go magnetic said that GPS isn't nearly as good because it shows your course over ground NOT your heading, so it will be impacted by the boat side slipping, current, and so on. My question is, have those guys who use the prostart (I don't personally know any of them to ask) just decided that the starting features are more important then the compass and therefore they don't really care that the COG isn't' as accurate in picking out shifts? Or do they have a way of interpreting the data that they get from the GPS that makes it more accurate for them? I know these guys are way better then I'll ever be. And likely very in tune to their boats... but I have a hard time believing that they are just so in tune with things that they give up compass headings all together.