It varies by brand and color, but quartz often runs a bit higher than mid-range granite, mostly because of the manufacturing process — though budget granite and premium quartz can land close together.
Both resist scratching well day to day. Quartz edges out granite slightly against everyday knife nicks, but neither should be used as a cutting board.
Not recommended — direct sun exposure over time can cause quartz to fade or warp. Granite is the better call for an outdoor kitchen; see our outdoor kitchen countertops page for that.
Warm water and mild soap is all it needs — no sealer, no special stone cleaner required, which is a big part of why people choose it.