I have BSA's with twin oval wound and twin flat wound springs, as fitted originally, and as available in the present day from J.K. etc. The 43.5 inch guns in .177 were fitted with twin springs, but the large 45.5 inch .22 "sporting" and Military both had large singles...that said, I have a pair of BSA opposite wound springs for a 45 inch gun with factory stamps (all genuine BSA spings had the pylarm mark stamped at the end, and their advertising at the time urged the use of genuine spares).

On firing, the twin springs (especially when flat wound) seem to give a softer recoil imho, on two guns with fairly similar M.V. ...but unless you poundage rated like for like to be exact, this is not really scientific. I normally polish and square the ends of all springs, and either polish the bearing area on the trigger block, or fit a delrin seat on anything old I take apart as a matter of course.

I have gone the full Monty on one oldie I have, and it is as smooth as a TX to cock and shoot....more recoil obviously because of the lighter weight, but silent and smooth.......but back to the O.P., I suppose a light hold and close observation of a gun trying out the two different power plants in succession would be the way to see for sure