Yes, marble and granite are porous, and no good stone supplier would suggest marble for a kitchen, because it is much more porous than granite. (Marble is okay for baths.) Yes, both need to be sealed regularly. However, while some spills will leave marks, all can be mitigated. For instance, red wine stains on a light granite can be removed by using a poultice (professionals only.) However, if you are the patient type, the stain will eventually sink through the stone and disappear from the surface.
The bigger problem is etching. Acids (citrus juices, alcohol, sodas, etc.) will etch the surface of a polished stone if not wiped up in a timely manner. It takes the stone people coming to re-polish the surface to fix it.
Stone will always be cold, so you have to be very careful not to set hot dishes or pans on it. Pyrex or glass cooking dishes can shatter, and metal pans will warp. Too, it you are serving a buffet, unless the food dishes are on trivets, hot food will not stay hot long.
That said, potential buyers see stone countertops as a value item. If there is a chance you will be selling the house in the next 5-10 years, buyers will see laminate countertops as a cheaper material and something that they will have to pay to have replaced, cutting into their offer to you.
Concrete is just as expensive as stone in most parts of the country, glass is seen as being too delicate, and while tile is a hard wearing surface, people don't like dealing with the grout.
Perhaps the better alternative is a quartz product. It will cost almost as much as granite, but because it is ground granite particles in a resin base, it won't require sealing and it won't be as cold to the touch.