My understanding is that PU is considered to be longer lasting than EVA, and it is EVA that is more prone to breaking down.  EVA tends to be used in lighter footwear like trail running/trecking shoes and some boots.  It may be a problem, specific to this model of boot, so personally I would not be inclined to exclude all PU cushioned boots for that reason.

Brasher for example has EVA cushioned boots, which I think are supposed to be fairly wide fitting (though I have no personal experience) - fit is everything and there is no substitute for trying them on.

[PS - I presume it is the cushioning that has disintegrated, not the tread worn out - if it is the tread this is nothing to do with the cushioning midsole]