I'm afraid I still don't get how A/P is any better than A/A, post SP failure. Lets look at two hypothetical arrays using round numbers, one A/A and one A/P. Each houses 1 TB of net storage divided into 10 LUNs. Each array has two SPs that can handle 1,000 IOPS each, and lets say the average and peak workload is 1,500 IOPS.
The A/A array delivers about 750 IOPS on each SP, but if one SP fails, the remaining SP can only provide 67% of the needed I/O. The A/P array also delivers about 750 IOPS on each SP, but if one SP fails, the remaining SP can only provide 67% of the needed I/O. How is A/P any more fault tolerant?