If you had a choice between the 3160 and the 4120QDC, get the 4120. I tried both, used the 3160 in a class at my local quilt shop (my besty works there). The 3160 is, oh how do I say it, cheap looking and plastic-ee. The 4120 doesn't look as cheesy as the 3160. The 3160 came out before the 4120QDC by a year, so I figure the 4120 just fixed what was wrong with the 3160. The girls in the shop didn't like the sound of the 3160, it was kinda noisy compared to the 4120. Just my opinion, I've tried both and now own the 4120.