Of the 4 you listed I've only had the Mortlach, and I love it. But I'm not hyper-sensitive to sulphur nor do I mind a bit of 'good' sulphur (sandy-mineral/leather/matches/flints/tar) in my whisky... the last 08 batch of the Mortlach F&F I tried had no noticable sulphur notes for me though.
But, there are slight batch variations, so might be there are some with noticeable sulphur traces in some.
Also, there's a pretty persistent rumour, or knowledge, I'm not sure as I haven't been to Mortlach and could see/taste for myself (or have it explained so I actually understand the what's & why's...), that their new make is slightly sulphuric on purpose, which is part of it's heavier, more meaty profile...
These sulphur notes of the new make usually get tamed down beyond recognition over the first week in the wood, but still contribute to the general profile.
So you might want to try before you buy if you get a chance.
If you have to buy blind, my choice would be the Mortlach, or maybe the Longmorn (admittedly, that might be the cask strength speaking to me...).