1.Out of the box, the sd1plus has more styles than Sd5.
2.Sd1plus has a balance mic input
3.SDplus has the "unplugged" feature, which means that you can choose a style, view the parts in the style and instantly isolate that part, making it unplugged. An example would be a style that has a good acoustic guitar strum, you can isolate that guitar part at the beginning of a song, than when you press the fill in buttons, all parts come in ...
4. The SDplus stores it's styles on the harddrive where as the SD5 uses internal "ram" ..up to 198 styles (with expantion chip) vs. hundreds of styles being accessed off the harddrive.

Just a few differences ... Dan O'