Mr Smith would, from his own mouth, appear to be either misrepresenting the PMs words, or illiterate.
He quotes the PM as saying: "...we should sustain the Tornado fleet as that aircraft is more capable and better able to sustain operations in Afghanistan."
He then states: "the aircraft is, to use the prime minister's words, "more capable" of operating in Afghanistan than Harrier."
Which, of course, is not what he said at all.
The PM makes two statements, both of which can be argued as being justified.
1. The Tornado is more capable.
2. The Tornado is better able to sustain operations in Afghanistan.
The first is justifiable on the grounds the overall performance of the Tornado and its available systems and weapons availability. That extends beyond those required for Afghanistan.
The second is justifiable on the basis on the numbers of available squadrons, aircraft and crews. The Tornado force has sufficient to enable operations in Afghaistan to be supported indefinitely while continuing to support other training and exercises and the potential to support other crises. The Harrier force does not. Quantity, as they say, has a quality all of its own.
Now you can argue each of those claims till the cows come home. But that's not the same as misrepresenting the position as stated by the PM.