A B737 is most likely going to "crash" (i.e. cause a big mess on the ground) if it has a double engine failure in any conditions.
A light aicraft, whether a single or a twin, can quite easilly be landed in a field in the event of its engine, or all of its engines, failing - as long as you can see the field far enough in advance to be able to set yourself up properly for it. It will not "crash" in the sense that you use the word.
A B737 is much bigger, heavier and faster, and would need a bl00dy great big field to be able to land in such that no one is killed or seriously injured. However, it has systems on board which are sufficiently resilliant to make this an extremely unlikely event - so unlikely that it is considered safe enough to allow the general public to use these aircraft for transport.
If the worst does happen in an airliner, the fact that it is generally much higher than a light aircraft (typically around 10 times as high) means it has many more options as far as where it is going to glide to. Although extremely rare, it's not completely unheard of for an airliner to have a failure of all its engines (e.g. due to fuel mismanagement) and glide to an airfield many miles away. I seem to remember hearing of one case where one of the pilots used to race radio controlled cars when he wasn't working, and knew of a disused airport nearby which was often used by the radio-controlled racers, and he managed to successfully land his airliner there when it ran out of fuel - don't know if it's true or not, but it's a good story! I would imagine - although I don't know for sure - that even in an airliner you would need to have good visual conditions to be able to do this.
FFF
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