The reality is this; once or twice a year you spray and wipe with “sealer” which is as difficult to apply as Windex (not very hard to do). Some stones never need to be resealed, ask your fabricator if your stone choice is porous or dense and your stone supplier will advise you as to what and how to apply. Once or twice a year is a worst case scenario for resealing frequency.
The upside of quartz is that it is consistent. It has slab of marble no fissures, no veins, and very limited inclusions. It handles heat well and never needs to be sealed. Most manufacturers of quartz offer a warranty. If you like consistent coloring and look then quartz countertops make an excellent choice. Many of the manufacturers are offering colors that are getting much closer to a natural stone look without the downside. Quartz is very hard, therefore scratch resistant. It like granite can scratch and chip. It is my opinion that quartz is less scratch resistant, but is more prone to chipping. The very hardness that makes it more scratch resistant does make it more brittle and prone to chipping. Conversely, granite chips can be repaired more easily than quartz.
Corian is a synthetic and once very popular solid surface counter top material. Today it is used less and less and the company behind the product, “Dupont” has embraced competing products and is behind industry giants such as Home Depot in regards to the sealer treatment that they put on their granite to resist stains.