Sony- The S and E series sound the same, however the S series has the speakers as well which do not sound so great, but ok sounding. When I shave, and on other such asks I use speakers, other wise I have some portapros. The sound of the Sony's are some what bass heavy and full. This sounds good with some sony headphones I have which I thought were too much on the high side, sound better with these players.
Sansa- The fuze/fuze+and the clip zip/clip+/clip have the same internal parts as well as far as anything effecting sound qaulity. So they sound the same. These have a good balance between bass and highs, the sound is somewhat thin. This makes for a good light easy sound with rock and more chill hip-hop.
Sony- The S series has more funtionality for students with the built in voice recorder. The player is also just really nice looking, so for in class just being in a pocket it is great and people will notice it when you pull it out. The E series is more affordable, but no voice recorder is a down fall. The External speaker is also nice on the S series for while shaving or brushing my teeth, and just to share music quickly and easily with friends in person. The lack of a slot for a micro sdhc card is what hurts sony the most here.
Sansa- Fuze+ has a voice recorder which I mentioned is nice. If you perfer a nice hear through sound relaxed and balanced for the office or home cleaning which looks like get this. However for a more active life style or hiking running, weight lifting, and some freerunning get the clip+ or clip zip. Light weight, it just clips on. Small and doesn't get in the way at all. It also has a voice recorder which is awesom for recording lectures. Sansa's also have a slot for a micro sdhc card. I used mine to move files from my laptop to my school computers all the time with a full 12 gb. I know the Clip+ was a durable little player, I dropped it hiking, running, flipped and had it fall pretty hard on the ground, it kept working and often the sctratchs just rubbed off. It isn't the prettiest player but more functional.
Over all If you want something bass heavy and are a pretty laid, the Sony's will be pleasing to look at, hold, and listen too. Still chill but looking for a nice clear balanced, hear through sound get the Fuze+. On the go active the Clip+ will have you knowing you made the right choice. I have my Sony and gave my clip+ to my mom. I am considering getting a new clip zip. The sony will need an armband however, and with a fixed amount of memory I am about to make multiple playlists on a thumb drive and and make my pick of music from the playlists in the start of my days.