We always had Polled Herefords and some Charolais mix for size. The beef we raised for our own consumption was raised in confinement with a controlled diet, which produced a good marbled prime beef. The market doesn't pay enough premium to justify this effort and expense in large volumes.
There is a big difference between proper marbling and fat. What went to market was fat, what went to the freezer was marbled. :)
We raise Polled Herefords and will generally expose a heifer to an Angus bull for her first calf and a Polled Hereford bull thereafter. There are some advantages to the cross breed (and there are some advantages to the purebreds), but carcas quality is indistinguishable. The single biggest factor is whether the market bear the cost of targeting for prime over choice or select.