Sinfield's goalkicking success rate in 2012 was 82.84 per cent,( compared to 69.64 per cent for Smith)...in a team that scores the vast majority of it's tries out wide.
He is by some distance the most composed and consistent kicker the game has ever seen under real pressure.

Did Sinfield play on his own for the Leeds Rhinos? No wonder they've won that many SL titles from 5th

His international credibility is a subjective opinion, yours is he lacks it. Most people would probably think that your opinion lacks credibility, especially the corner you have painted yourself into regarding England and Leeds Rhino’s especially has led to some fairly incredulous opinions that you have put forth. But both my opinion on your credibility and yours on Kevin Sinfields are irrelevant because it is impossible to say what would have happened because they didn’t play, it is unarguable fact, that Australia’s decision not to play, and the disappointingly potical proposal from NZ did deprive Kevin Sinfield of the opportunity for international success against the major southern hemisphere sides and as such it is clearly correct to say that it wasn’t his fault he didn’t have success against those nations this year.

Sinfield did experience international success this year by the way. The international game doesn’t start and stop with the Australians, however much they, and their fanboys believe it does.

Perhaps he was denied. He's won MOM the last two times England have played New Zealand over here. If we could've had a 3 game England vs NZ series their's a good chance he might have been Man of the Series.

Who awarded him Man of the Match in the game played in England?