I came from a ramps setup and I too was at the smoothie/duet crossroads at one stage. A few things swayed me towards the duet.
a friend of mine had the duet 1 and I liked the macro ecosystem liked the web interface I seen an exchange on the reprap forum between dc42 and the developer of smoothieware which left a bad taste in my mouth for smoothie. the duet community is helpful and friendly, from an outsider looking in I found what seemed to be a more aggressive community in smoothie support on the fly configuration is the best, so much freedom for your machine