I have some Dia Compe center pull brakes shown below. I was wondering what the best type of brake pads are to use for these brakes. Looking around at pictures on the internet, many people use standard road caliper pads, while others use old style pads rectangular block pads (as in the picture) to preserve the authenticity. I've also seen a few examples of people using v-brake pads. are there any advantages to using a specific type of pad on brakes like this? I really don't care about esthetics, and I'm really just looking for what will provide the best braking experience.
You can use V-brake pads, but they tend to be longer and can create clearance issues. On the bike I currently have set up with those pads on Dia-Compe centerpulls, the shoes hit the fork when the brake is open, making wheel removal difficult.
As ojs notes below, road caliper pads are probably your best bet. They also tend to be on shorter posts, so they don't limit tire clearance as much as V-brake pads.
Back when those were The Brake, the pad to use was the Scott Mathauser pad. The compound was soft, reminiscent of a pink pencil eraser. While no longer made, there are several brands that offer similar compound: Yokozuna and Kool-Stop come to mind.
You will likely have to order pads to fit those calipers. It does appear as if Yokozuna actually still sells the blocks that are installed in the pair of Dia-Compe Gran Compe calipers that sit untouched since the late 80s in my parts bin. http://www.yokozunausa.com/screbl.html
That pad style is similar to Campagnolo, so if you have an LBS that stocks Campy stuff, you might be able to get something similar and install them.
Koolstop makes a bunch of different shoes and shoe assemblies. I'm pretty sure the Weinmann shoes will slip right into the shoe holders. Or you could replace the whole assembly with something else. Just about anything with a threaded post should fit those brakes.