It will most likely stay based in Canada. That's not for patriotic reasons, or even marketing. The fact is that a lot of retirement funds have shares in Molson. Those same retirement funds have restrictions on foreign foreign investment. Coors does not have a similar situation with its shareholders.
If Molson/Coors is operated out of the US a lot of stocks would be sold in order to meet the foreign ownership regulations. That would affect the value of the new company. To avoid that they must keep up the appearance of being Canadian owned and operated.
Of course the truth is that Molson has been a multi-national for decades. It is based in Canada, but stopped being a truly Canadian company years ago.
As for taste...Coors is the mass-market beer I'm most likely to buy when (if they let me in again) I'm in the US. Canadian has been the mass-market beer I've chosen in Canada since stubbies were mandatory and 2-4's were illegal in Saskatchewan.
I tend to drink a lot of imported beer (mostly British and Irish) in the bar and micro-brewed beer at home. I think that's become a pretty common pattern among a lot of people, which is why Molson and Coors have been losing market share in their respective countries for years.