Realistically... if your disc is below your service limit I'd replace it. When below the service limit you risk disc warpage from over heating... less mass heats up quicker and to possibly higher temp for same swept area.
If above service limit... dont! Technically, the disc should be machined to a fresh flat "run out spec' surface for the new pads. The cost would be probably around a new disc? A new disc would be the preferred option IMHO.
As far as pads go... I replaced my stock pads the day my Jackpot came home. I have used Lyndall Z-plus.
This from Lyndall....
LYNDALL pads are of the Carbon-Kevlar variety. They contain a premium blend of DuPont Carbon-Kevlar, nonferrous metal with a high transfer rate. Once the pad material has transferred a layer to the rotor, the rotor becomes one big brake pad, stopping against the two smaller brake pads positioned in the caliper. The result: incredible STOPPING POWER, NO DUST, NO NOISE, NO DRAG, NO MEASUREABLE ROTOR WEAR, and the HIGHEST SERVICE LIFE of any pad on the market.
To develop the Z+ compound we started with a racing brake pad material and worked our way backwards. We wanted to provide the optimum stopping power that was suitable for everyday general purpose riding. Our Z+ pads are a DuPont Carbon-Kevlar (organic) compound that will work as well right out of a driveway as it does after a long day of hard riding. This is the most rotor friendly pad in the industry. It produces no dust, no noise, while providing 20% more stopping torque than the stock pads. The service life generally averages about 18,000 miles.
The pads took a fair bit to run-in and be very careful when you apply any brakes first time after fitting... you dont have the braking power afforded by a bedded in rotor/pad.
I'm getting minimal dust and after the bed-in have great stopping power considering I have only one disc at the front and 650lbs + me!
I purchased them because they coat the disc with material giving far less or near zero rotor wear... and minimal corrosive dust. Extra stopping power is excellent to have as well.
I cant say they are better stopping because I replaced them before ever needing to stop hard on stock pads. Only 24 miles from my dealer to home.