I was always in the opinion that barley variety matter.
Look at Weyermann German Pilsner, Bohemian Pilsner and Barke Pilsner. Different barley Malted in the same facility (most likely the same way) {I could be wrong}.
My position remains that variety matters, and yet does not. Let me explain. A good maltster, with a good process, can make better malt from any barley variety than an inferior maltster can make from the same barley. A truly inferior maltster can still make poor malt from the best barley. So within a given maltster's range, a certain variety may be preferred for certain properties. But one maltster's best product may be inferior to another's most generic grade. To make the best beer possible, you need the best ingredients available at the time. For me that generally starts with choosing a trusted maltster, then deciding if a certain beer demands a specialty product from their range, if such a product is currently available. So I think the question posed in this topic -- whose MO do you prefer -- probably will point to a maltster any of whose products you would find superior to the products of other producers, maybe even to the extent that you'd prefer their basic pale malt to another's MO. Variety is not magic; each malt must be evaluated on its own merits.
PS. I currently am fanatical about the Weyermann Barke line, Thirsty_Monk.