I have both, I like having both
I reckon at some stage I might give up on Dopus cause of the upgrade costs. I am more used to DOpus though, and it is more, eh, comprehensive - and I've invested lots of time in customising it over the years (XY is a much more recent aquisition). But out of the box I actually prefer XY (but really I'm no power user of either app).
XY is very
portable, with "Portable File Associations / Portable Openwith Menu" - fairly easy to setup. I love the Portable Openwith Menu.
Search is super fast.
~ Some features I'm not so familiar with -
A good list of features (with links to more detail) here
Also, with XY you get great "software-satisfaction" from the amount of updates... :-)