http://velonews.competitor.com/2012/...-faster_209888

25s or 28s have lower rolling resistance than 23s. You will not sacrifice speed. The wider tires do increase drag, but for the riding you're doing with the wheels that came on your bike, that shouldn't matter.

+1 on dropping the tire pressure, too.

As for which tires to get, I've been happy with the Bontragers that came on my bike, but I don't know offhand which model they are. I've had other Bonti's in the past that were more prone to flats.

I've also been happy with Continental Gatorskins. My main concern is avoiding flat tires. I had some Vittorias a few years ago that rode like butter, but I had too many flats with them and the sidewall started to peel off after only one season of riding.