DY is the only LCC I will fly (and forced to occasionally by my employer...) in Europe. As fassy says, not much difference between them. I find staff on DY to be quite OK. The only reason why I try to avoid DY (vs. SK given I have status) is the unbundling. I also actively dislike the 737 as I find the 320 to be a far superior experience given the bigger cabin. And do not like that DY flies the Max which I avoid.