I can understand your concerns.

I do not have the same problems as you since
I and my dogs are staying put, but I will
let you know what I feel having a multiple dominant
dog house.
Draw backs:
I personally will not have 2 dominant dogs in a household
again of the same breed.
Now, you are a lot younger than me and probably
have more patience and energy. lol
But because of their dog dominant issue, I can not
walk them together, and taking them on vacations
is a lot of work.
I must walk one dog, than come back and walk the other.
All 3 dogs get jeolous of each-other and I have
to be careful to make sure a fight does not occur.
Not to mention the expense of
vet bills and food. To be fair I have
2 AKita's which are a stubborn, dog dominanat breed.

On the "plus" side of having 2 dogs:
They keep each-other company.
And if both dogs are not stubborn, and not dominant it can
add joy to your household too.

I would definitly get the opposit sex dog, and
if you can, (no guarrantees) try to find
a puppy of a breed or breed mix that is
not of a stubborn breed, (helps with training)
and has no dominant issues.

JMHO