In GS finals that is maybe true, but look at the semi against Djokovic at the AO this year. He was a set and a break down, managed to get back into it and again in the 5th set he was 5-2 and got it back to 5 all. In the past he maybe would have fallen apart in that match but this time he never.
Yeah I said with the exception of that match mate but no question he choked badly against Ferrer.
Yes Ferrer is the better player on the surface and in sparkling form whereas Murray hasn't been great the last few months but still, the manner of how he goes about losing is antonishing.
Last year at Flushing Meadows he was literally choking away a potential victory against Nadal on a surface he should own Nadal on. Instead, he gets blasted away in 4 sets that were not even close.
A few months later, on a similar surface in Tokyo, he loses the first set then goes on to win 12 of the next 14 games including bagelling Nadal in the final set en route to the title.
In Grand Slams, its hard to find anyone who has choked more than Murray.