Personally I don't understand why you would want a U/O if you can own a semi auto with no special permit as you can in the USA?
I'd trade my Miroku for one any day if I could
Weight and balance mainly. My Citori is a heck of a lot lighter than my Browning Silver. I usually cover 10 miles a day, so it makes a difference. And a quick handling 28ga when hunting grouse is just plain fun!