IMHO .... like the answer to many strategy question is .... it DEPENDS!
It depends on your fitness goals. I believe you would benefit more
aerobically from the 60 cycle time, and you would benefit more
strengthening by 90 second cycles.
BTW, I believe the same applies to the number of sets you do. Fewer
sets with higher turnover rate between means more of an aerobic
workout ... more sets for stressing the muscles deeper and more
thoroughly.
Hope this helps.