If you're up in the air about which one to get, why not get the SB3, that way you have the display, and can add the duet's remote later if you want/need it.
I have an SB2 that I bought years ago, and the thing is great. It is really the most convenient thing I ever did for my music collection. I coupled it with a Thecus N5200 that runs squeezeboxserver so I don't need my computer to listen to tunes, the box just sits in a closet with all my music files and hums away.