The resolution is a touch low and there does appear to be a slight variance in the scan dynamics, but it's probably OK.
B shows more scatter and less definition than A in the cyan nozzle check. A has more definition and generally higher density. During the B print one of the nozzles had a partial deflection.
Undoubtedly neither check is showing an empty or virtually empty card - ink supply is consistent.
A has more consistent dot gain but it's slight.
Overall they are indeed very similar, I agree. However, A is better than B and I would suspect that was your "bad" cart and it appears to be less consistent. This could be separation, although generally the smaller carts are much less likely to suffer this, so it could also be that you had a slightly bad seal and a touch of air getting into it. If it happens again with the new cart at some point, you may want to look to see if there's any dried ink or other detritus affecting the seating of the cart in the holder or affecting the deal.
A first hand examination would be better, though, particularly given the slightly inconsistent scan. Also, hold on to your "good" check for future reference as that is really very useful. In this instance, with the scans available, it's inconclusive but my suspicion is as above.