Personally I think smithfields are over injected. I'd much prefer to get a slab from a butcher shop that is not messed with.
This slab cut in 1/2 was 7 1/2 hours total cook! No where near dry.
I'm not a box store shopper, so I cannot attest. As far as "store" brands, I have found that trimmed st louis from Target are pretty darn good and meaty.