IMO they're apples and oranges.
IME strength gains have a much higher ceiling than "cardio" because with proper training and diet, most people can substantially increase muscle size and strength for years. But it takes many years of dedicated training to achieve your genetic max for strength. There are many instances of dedicated lifters increasing their bench and squat every year for 10-20 years after age 18. A novice lifter will almost always make faster relative gains than an advanced lifter but in absolute terms, of course a previously advanced lifter will more quickly get back to a 500 lbs bench after a break in training.
For cardio, once you've achieved healthy weight and body composition for your sport (that's the rub for most "untrained" people), there's a much smaller range for VO2 max improvement and you're going to hit the inflection point of diminishing returns much sooner than in strength training. "Muscle memory" is also a little misleading because in general the less muscle mass you have, the better your cardio will be for LISS.
In the military I saw a lot of otherwise healthy 18-25 yo kids that had to comply with height-weight standards and 5 day/week group runs. On the PT test days, you'd see a lot of guys with the same height, weight and approximate body composition, who had all been doing the same prescribed group training and had the same diet. Run times were all over the place. IMO any healthy man under 30 yo should be able to run 2 miles under 16 min with proper training. But some guys just can't break ~13 min even with dedicated training and they're already skinny with low bf% and physically resemble competitive runners.
