I dont think i really need to say which amp i'd choose between the Mac & Bryston
On a serious note ,as you said both amps are beasts & built to last forever so your choices would have to be based on personal preferences like resale,looks ect.
The MC402's resale value has gone up steadily since its release & should continue to climb for a few more years,The Bryston's resale value is good too but it has not gained any real value.
As for looks i believe that at the price point manufacturers charge for high end gear the equipment should look like more than a black box with no style,any 4k amp should scream class.