Quarter sawn wood is more resistant to splitting. That is why it is the preferred material for pinblock and bridge caps where resistance to splitting is most critical. Quarter sawn pinblocks usually last 50 or more years. It is also believed to transmit energy better making it superior for bridge caps and soundboards (spruce).
Quarter sawn wood is more expensive because there is more wastes associated with its manufacture. It is generally more difficult to work with since that usually involves cutting and planing againt the end grain. Steinway used and still uses quarter sawn pinblocks. Mason & Hamlin and other high end piano makers used quatersawn maple pinblocks. They also usually used quarter sawn bridge caps.
Quarter sawn maple bridge caps are easy to pick out. If you look closely at the bridge from above with good light the wood will appear to have little red dots on the top of the bridge. If the red dots are on the side that is a flat sawn bridge cap. The pinblock is not so easy to see visually.
The lesser quality older piano used flat sawn lumber. They often had 10 or more layers. Flat sawn pinblocks might last 50 years or longer as well, but asually the quater sawn blocks last much longer that flat sawn ones.Many newer pianos today have what are known as multi-laminate pinblocks. They are contructed using many very thin layers. They are bonded using modern high strength glues and are really, really strong. They are heavier then ther more solid wood counterparts. Baldwin uses a pinblock with 41 layers. Delignite is another popular German brand used by Charles Walter pianos and othes. They seem to hold up well, but since they have only been used in the US for about 30 years the life expecancies of these materials is not fully known.
Piano rebuilders use all differant materials. When having a piano rebuilt it pays to know what kind if materials are beening used. Quarter sawn pinblock material is usually the most expensive, next are the multi-laminates, the flat sawn bocks are usually the least expensive.