steel is stronger by far but it depends on the situation.when we started out on certain jobs , big ones, where weight mattered the handrails would be ally, not steel.you dont need strength in a handrail, after all its a barrier.
ally is not as strong as steel so yes you need more in a comparable area but the point that matters in this day and age is ally is DEFINATELY more likely to be stolen for scrap or by another scaffolder (possibly the one you pay to put the job up) so any one thats going to use ally is crazy
when you come to pay for the missing ally at the hire firm, with their prices you will wonder if gold bullion wouldhave worked out cheaper.
hire steel,
count every tube, board ,fitting and ladder delivered to your job and count them back on when its returned
if the boards /tubes have mortar muck on them from the previous hire record on the delivery note in the comments box ,or just write it on so you dont incur a cleaning charge