I think it was enormously sensible for both countries to persue their own indigenous designs 'just in case', both did fantastically well from a practically standing start too. It's often neglected slightly just how much materiel production Canada lent to the war effort, from trucks to valentines the figures are enormous.
One little snippet on indigenous designs, it was even considered by the British (1943ish? I'll have to check) that it might be worth dropping
all indigenous armour projects (Cromwell, Comet etc.) to concentrate solely on the Centurion and relying wholly on US imports until that very promising vehicle was ready.
Now there's a 'what if' for people to have pointless arguments about
.
Cheers,
Adam.