He lost speed but gained wisdom n size after his long layoff. Ofc after 74 he was descending into a downward spiral. Thrilla in Manila took so much out of both fighters its impressive Ali was able to compete at a high level still afterwards even if just briefly. The man who beat Liston, Patterson, Terrell, Williams,etc was long gone by the 70s tho ofc he's shown many moments of brilliance still. Very durable one of the most but he relied on that trait too much in the 70s imho. Many punches he really should've avoided especially since he was easier to hit in comparison to his peak.
For me it was clearly the 2nd Norton fight, as i said in your other thread about Ali. Ali kept up his amazing footwork for all 12 rounds, looked at his fittest ever for the 70s IMO. Ok it wasn't a dominating performance, but considering it was vs an opponent who had a poision style for Ali. For me it was Ali's best performance in the 70s, regarding coming somewhat close to showing the attributes he had in the 60s.