Get them both at 20% off. Don't forget that these discounts stack if you pick them up as part of the D&D Complete the Set Bundle. If you have any friends who are on the fence about picking it up, now is the time to let them know.
http://store.steampowered.com/app/360115/?snr=1_5_9__405
Get the D&D Bundle at a discount and get every new addition to the bundle at 25% off as well. That means you can pick up the Volo's Guide to Monsters for 25% off at launch.
http://store.steampowered.com/bundle/256/