Both are relatively easy to learn, but hard(er) to master. How long to master it? I don't know. I haven't used HS that long yet and I'm still learning new stuff in Daz regulary.
Choose HS if you have slower hardware, use HS if you don't have much time, choose HS if you have a AMD grafics card and don't want to buy a NVidia.
Choose Daz if you want to get great grafics for your game, have or want to get an Nvidia card, have good enough hardware in general.