OK.....drumroll, please....
I did the Great Brat Experiment. Disclaimer- I am biased towards grilled raw brats, unpierced, stirred, not shaken.
I divided 6 Vollwerth's brats into 3 groups. Group A was grilled unpierced on med-high for about 12 minutes until med to dark brown on the surfaces exposed to the fire.
Group B was pierced, simmered for 30 minutes in 12 oz of MGD with 1/2 of a sliced yellow onion and then grilled until brown for about 5 minutes. The precooked weight of the two were 172 gm. After the simmer, I strained out the onions and put the liquid in the fridge to congeal the fat. The fat weighed 4.5 grams and the brats weighed 152 gm before grilling.
Group C was grilled the same as Group A but then put in a beer/onion bath at 180F for 30 minutes.
The results were divided between 4 tasters who were allowed to use buns and the same condiments for all groups.
Group A had a very good texture to the interior, a satisfying 'snap' to the casing, and sweet carmelization. Rated 4 buns up.
Group B had a noticeably denser, drier interior texture. The casing had a 'snap' but wasn't nearly as sweet as the first group. No one could detect any flavors of beer or onions. 2.5 buns up.
Group C was very similar to B except that the texture was a little better but the casing 'snap' and sweetness was absent. Two people said they could taste the beer and onions faintly. 2.5 buns up.
The interesting thing is that there was hardly any fat lost in precooking so it is not a way to reduce fat in you diet. Brats are 1/3 fat and if you want to reduce fat, don't eat brats.
Most of the weight lost in precooking is water resulting in a drier texture. There was no absorbtion of the stewing liquid, hence lack of additional flavor. Just because meat is close to liquid doesn't mean it will be moister. Remember Mom's pot roast?
Most cheesehead sites recommended light beer. I don't get why people buy beer without beer in it. It only encourages them to make more. Heavier beer would seem to be the obvious upgrade but there is a problem with cooking with beer in general. It is the hops. Hops add three things- aroma, flavor and bitterness. As you cook hops, the flavor components convert to bittering compounds making it a really difficult ingredient.
On piercing...Johnsonville runs a commercial showing a brat noob getting ready to poke with a fork. He is intercepted by an older, wiser gentleman who trades his fork for a pair of tongs.
So, you have the results of my unscientific, highly subjective, non-double blinded study. I know that brats are like politics and religion in that you are indoctrinated early on and spend the rest of your life trying to justify your beliefs. There is a time to mix brats and beer.... in your stomach.
Pass the kraut and mustard,
Kit
duck fat rules