No worries.
I just think that the MM is more scooped and has more lows than the CS. I have the CS in one of my SGs and I am thinking of trying a MM in there next just because that pickup has fascinated me for a while and the CS doesn't really hit those heavier tones.
I would say that the CS is great for everything from Judas Priest to Pantera. Old school DM perhaps to go a little more bassy, not a huge amount, but enough, and with more overall output. To me it seems like the mid scoop in the MM would be bigger, with more highs and more lows. This is the impression I keep getting of it from reviews. I have also seen people with maple necks recommend it a lot, which is one reason why I thought it might work for you.
I have to admit that I have not been consistently impressed with the recommendations of the BKP staff recently. I think that they can give good recommendations, but that this depends largely on the way the question is put to them, which basically involves telling them you have this or that guitar they are familiar with or a combination of woods that they have a lot of experience with and can either give them a clear account of precisely what EQ stuff you need or relate it to a genre that they are are very familiar with. I suspect that they haven't spent a lot of time listening to Possessed, Celtic Frost, or Autopsy and when you say 'old school death metal' they just think 'EMGs'
I personally cannot imagine the HD being an improvement on the CS for this application at all.
I also tend to think that the BH will give too 'deathcore' a sound for what you want
