The best way to decide is to go to a shop and use both of them. You cant decide over net which would feel great in your hands.
Its a matter of personal choice like I like mobiles having some weight, so I like XE more than S2.
I love Sense so for user interference my vote also goes for XE.
Lastly I love Music so again my vote goes for XE.
It doesnot mean that S2 is bad. I liked S2 for its speed,simplicity and being light weight but I hate its build quality.