The short answer: you should, theoretically.
The long answer: both kits feature 13" rotors, but the Cobras are usually sold with vented rotors whereas the Rs are at least vented and slotted, if not cross-drilled too.
The four piston caliper on the brembos are what will really make the difference compared to the two piston Cobras.
Whether they are worth twice the price, I'm not sure.
I believe one of the auto mags just did a high-performance head-to-head test of a 2000 R and a 2003 Cobra. I can't be absolutely certain but I think the 2003 was pretty close to the considerably lighter 2000's sixty- and eighty-to-zero distances.
Those four piston brembos sure do look pretty, though.