Well then......
Don, Wisconsin is my home away from home. I can't tell you how many saloons, restaurants, campgrounds, resorts and hotels I've been to in Wisconsin thru the years. But so many so I should be able to vote there!!
In my travels I've had a lot of good brats, but found THE VERY BEST bratwursts that I've ever had comes from the award-winning butcher shop Miesfeld's Meat Market in the home of bratwursts, Sheboygan, Wisconsin.
Here is a link from Miesfelds on how-to cook the best brats!
www.miesfelds.com/wp/grill_tipsSo my vote is NO parboil unless cooking for a big crowd!
In that case brats are cooked over coals and HELD in a broth of beer, sliced onions, and butter.
This is getting me hungry and thirsty!