There is no advantage to going with narrower tires. In a 'performance road bike' context, 28mm is not really narrow, but obviously narrower than what works for you.
I am about your weight and personally don't see any reason to go narrower than 32mm tires. That allows me to run at a bit lower pressure than with 28s or narrower, and are still reasonably light.
FWIW, the old theory that wider tires have higher rolling resistance has been debunked. Rolling resistance is a result of the tire casing deflecting as the wheel rotates, and narrower tires have to deflect more than wider tires. All other things being equal (like you find two sets of tires with identical construction but different widths), you will have slightly less rolling resistance from the wider tires, but better shock absorption and traction.
Narrower tires are generally lighter (helps a bit on clmibs and while accelerating), and the narrower profile causes less aerodynamic drag at speed, but in most situations for non-racers it doesn't make any real difference.
Also, while you enjoyed your Bontrager tires, I bet if you found a set of less robustly built tires (my favourites are Panaracer Paselas) in the same size, you would find them much nicer to ride. You may get flats more often, though.