In threads of this type one of my arguments is that the Spanish naval bases of Cadiz and Ferrol were closer to the trade routes (especially in the South Atlantic) than the captured French bases on the Bay of Biscay.
I've tested my theory by using Ports.com to calculate the distances from Brest, Bayonne, Ferrol, Cadiz and Las Palmas to Halifax, New York, Port of Spain, Freetown, Natal, Buenos Aires and Cape Town.
This was the result.
Then I re-arranged it like this.
Ferrol is about one day's sailing at 10 knots closer to Halifax and New York than the Biscay ports, but it's only a reduction of 5-10%.
OTOH (and not altogether unsurprisingly) Cadiz is about 3 days closer to Port of Spain, Freetown, Natal, Buenos Aires and Cape Town. Las Palmas is even better with a reduction of 6 days at 10 knots. Furthermore, the reductions are bigger as percentages of the journey times from the Biscay Ports. In the case of Freetown there's a 25% reduction from Cadiz and a 50% reduction from Las Palmas. The reduction in the time taken to reach Natal is reduced by 16% from Cadiz and 32% from Las Palmas.