Oboe reeds are sometimes, not always, classified as soft, medium, and hard. The difference is that in soft reeds, the reed opens quickly under a small amount of air pressure; in a hard reed, air pressure needs to be more powerful. Hard reeds have more cane material intact, and are more difficult to play without training. As long as the player is properly trained in woodwind playing technique (embouchure) a hard reed will produce the same tones as a soft reed. A hard reed also might last longer because of its extra structural stability. For learning embouchure, most teachers recommend a medium reed, so that bad habits from a soft, easy reed won't form, but soft enough to produce notes without struggling. To sum up, a soft reed is easier to play but may be less durable and might foster bad habits in beginners; a hard reed is harder to play but will ensure better technique, and might last a little longer. None of the information I saw shows a substantial audible difference in tone between hard and soft reeds. With the proper instruction, a player can also use a sharp knife to scrape the reeds, which will alter the tone to a certain extent.