How would Argentina fare against the larger postwar Royal Navy?

How badly would this timeline affect Argentina's naval balance?

Badly, because a larger Soviet fleet would likely keep the Royal Navy larger and might preserve or produce a later British battleship class.

The Royal Navy would begin this timeline's war, if one occurs, from a larger force and would continue measuring itself against a stronger Soviet navy afterward. Britain might still retire its old battleships, but it could retain a later class or build a postwar successor that never appeared historically. Argentina would therefore confront a materially less favorable balance than it did in the real postwar era. The precise fleet cannot be predicted because the war itself changes, but the direction of the imbalance is clear.