That's like asking what's the difference between good music & bad music
It's all a matter of taste, I suppose...I was just passing along something I heard that might be germane to your project. Very much related to the fact that luthiers don't use the cheapest woods they can get, they use woods with good tone; even solid body electrics are affected by the tonal quality of the wood. It stands to reason (at least to me) that speaker cabs would be just as sensitive to the grade of wood used, allowing for the fact that baffles are used to keep things from getting too lively. I assume your goal here is to replicate, as best you can, the beautiful tone of the early Sunn cabs, w/o putting yourself in the poorhouse with EvilBay's help; I feel safe in guessing that Conrad didn't cut corners by using the cheap stuff from 84 Lumber
Not for nothing, I really do hope your project is everything you're hoping it will be; I'm not an expert, I'm not here to lecture, just sharing what little knowledge I have to spare
And if it doesn't work, hey, it's a learning experience...