What type of finish is best?

This is a question that there is no universally-agreed upon answer to. We prefer the traditional oil-base polyurethane finish, which is a very durable product. It has an amber coloration that intensifies the underlying coloration of the wood, and gradually darkens over time (but may fade in areas of direct sunlight). It has a noticeable odor following application, and generally needs to dry overnight before foot traffic or re-coating. Waterborne finishes are becoming more popular, but are generally not as durable as oil-base finishes (there are some commercial grade waterborne finishes that are very durable, equaling or exceeding the oil base products). Waterborne finishes are more expensive than oil base, have less odor, dry more quickly (typically dry to foot traffic in 3 to 4 hours), and impart a very light color, nearly a bleached look, to the floors. Newest generation prefinished products usually have an aluminum oxide finish, which is the most durable finish available. This type of finish is not available for site-finished floors, since it must be applied in a controlled environment and subjected to ultraviolet-ray curing immediately afterward. (When you evaluate the extended wear-through warranties for these products, some as long as 25 years, keep in mind that the manufacturer warrants only that the finish will not wear through to the wood during normal abrasion from foot traffic; you will still experience dents, scratches, dog’s claw marks, erosion from chair rollers, dulling of the finish in high traffic areas, etc., all of which are not covered under warranty).