The Legend coupe and GS sedan rotors are the same diameter as the V6 Accord rotors at 282mm (11.1"), but they are thicker at 28mm vs. 25mm. There are larger rotor options from the '99-'04 3.5RL, '99-'03 3.2TL and '01-'03 3.2CL at 300mm (11.8"), but those will require caliper brackets from one of those models as well and are not required when swapping the 2-piston Legend calipers on a V6.
They are a larger upgrade in comparison to 4-cylinder cars than they are V6 cars. In fact, in some respects, they're not a straight upgrade for the V6 cars. An important figure when comparing clamping force is piston surface area applying pressure on the pad and, in turn, the rotors. The V6 Accord caliper has a 57mm piston. If we agree that the surface area of a circle whose diameter is 57mm = (57/2)^2 x 3.14 then we get 2551mm^2. The Legend calipers have a piston size of 38mm and 42mm. [(42/2)^2 x 3.14] + [(38/2)^2 x 3.14)] is our formula and the total we get is 2519mm^2. That's less surface area than the Accord V6 caliper! Now, that's not the only only dimension worth caring about. The benefit to the Legend caliper is having that surface area more evenly spread out on the same exact pad. This will help to decrease brake fade and prolong rotor life. Honestly, most people just care about numbers, though, and 2-pistons is better than one. That's usually all the convincing some people need. That said, I have a box full of 2-piston Legend calipers at home and when I throw the 300mm rotors on the CG2 I have before I sell it, I'll likely put the 2-piston calipers on as well.
