Both are relatively easy, but quartz is the easier of the two. Granite is porous, meaning it will absorb liquids over time. This requires them to be sealed yearly to prevent damage or discoloration in the stone. Quartz, unlike granite, is non-porous, so it requires no sealing.
Neither countertop likes harsh chemicals or highly acidic things, so you must quickly wipe up spills (lemon juice, tomato, wine, coffee, vinegar, etc.). And granite is more easily scratched than quartz, you want to use something non-abrasive to wipe it down (e.g. microfiber cloths). Granite also is more prone to chips than quartz.