Always grill first... Low and slow... "The Charlie Murphy Way". That dark brown hue is what you seek.
Klements brats are very good as well.
But Johnsonville is the "quintessential" brat.
I like mine in beer and onions AFTER the grill, then on a good brat bun with bit of raw chop raw white onion and brown or stone ground mustard.
Enjoy your summer grillin'!