You might want to play with SLic3r's settings a bit before you make your decision. I started with Slic3r and used it for almost 10 months exclusively. I know it can do far better than what your pictures are indicating. I do use s3d now and it does do many things better than slic3r (in my opinion) but slic3r has its own merits. Surely slicing software is important and it can make a difference but, as I've painfully discovered recently, if something is not going right there is a good chance human error has at least some part in it . Even minute details/changes can have drastic effects on print quality. Before I switched to s3d I performed a similar experiment and also discovered that most of my prints looked better using s3d. But the difference was not quite so drastic as yours. Perhaps your slic3r settings are not as refined as s3d?

I'm not trying to "preach" or guide your decision. I Just wanted to suggest that if something looks off in your prints, think about what the cause could be: over extrusion? Under extrusion? Temps not quite right? Sometimes changing one thing (a speed, a temp, e-steps) has unexpected results. This is an exciting and deceptively complicated hobby. Good luck :-).