Hi!
My 2p
The full speedbrake deflection of the A319 is about as effective as the half-one on the A320 and A321 hence the longer time needed to get down.
Then about cabin leakage rates:
There is no significant difference between the three. The A319/A320 should do no worse than 900 ft/min and the A321 no worse than 850 ft/min.
Rgds