What is the difference between the 15-day and the 60-day disabled list? Two things: The 15-day DL players are
Teams assign players to the 15-day and 60-day lists according to their individual needs and judgments. You cannot infer too much from a player's appearance on the 15-day DL. A player on the 15-day DL will not necessary return to action soon, or even before someone on the 60-day DL. For example,
It's important to periodically scan the injury reports to see who is rehabbing and ready to return versus those facing months of uncertainty. Many leagues provide a DL spot, which helps, but you still need to make tough choices. During the course of a season you have more injured players than DL spots. Sometimes you have to keep an injured star on your roster; sometimes you have to bite the bullet and let him go.
Players on the DL that are returning in the foreseeable future with good potential to contribute are for better. Players will uncertain futures, murky diagnosis or limited upside are for worse.