The SD3 is the module version of the SD5 and so has all the same styles.
The SD3/5 has some advancement in sound and technology over the SD1, but also lacks a good number of the features available on the SD1. (The SD3/5 is a midrange board, whereas the SD1 is a top of the line board)
If you wish to stay with Ketron (Which have always produced impressive boards) wait until the Audya is released, as this will be the true upgrade from the SD1.
Hope this helps

Bill