I agree with what your write Pike, and I would also add this to your point about short careers:
going from a leading club in a middle or low tier league to a middle or lesser club in a top tier league to be sure means that you will win less but you will get the chance of playing against some of the top top players of your time. Besides the stars and the journemen, most players only get one or two chances of doing that. For 2-3 years you get to measure yourself against some of the top footballers, to put yourself to the test, be part of the elite of football (although only by association :)). IMO, that should not be underestimated. I know it's one of the standard interview things to say when you come to a new league (it's the best in the world, blah blah) but I do think most of them mean that.