A logical person might think that a bottom bracket with longer spindles would use better/stronger bearings, but maybe this is not the case here. Yeah, an overlength spindle could hurt the bearing life, but there is really nothing you can do about the spindle length. If Shimano doesn't make the size you need, your choices may be very limited.
As far as cheaping out on components goes, the BB and the front hub seem to be the places where even "better" companies, such as Giant, do most of their cost-cutting.