I carried a pair of pbm 6.5's around to every studio I worked at for four or five years during the naughty nineties. I found them to be much better sounding than the ever-present NS10m's.
Here's the bottom line: the Wharfedale Diamonds are powered where the Tannoy's are not. That takes one more variable --- the power amp --- out of the equation, and will mean that after I buy my own pair of the Warfedale's I will be able to enjoy even more consistency in my mixes.
Get the Wharfedales.