Jackonicko
There is one major difference between Sioux city and the Concorde crash. The Sioux city had to land - one way or another - and their situation was never going to improve. They had no choice. Besides their speed must have been considerably slower when they went into the corn field. The speed would also be much slower on an overrun accident.
My guess would also be that Concorde pilot doesn't recieve any training in forced off runway landings. They are probable thought to have confidence in that the plane will keep flying (which would probable also have been correct if the limitations and procedures had been observed). Also the aircraft was on heavy fire and had loads of fuel. Landing off runway with no immediate fire service would probable have meant they would have died anyway, so I would have fought to keep it in the air as well.
GlueBall
I know. But there is a major difference between an almost uncrontrolable delta wing on flames going 200 kts, and a perfectly good and controlable B737 with a stall speed of 100-120 kts.