For me it all depends on what year and model you are comparing .
I like an Alloy base that won't break easily and certain models have more alloy and reinforced skirts.
I remember reading somewhere that the early petrol alloy base Sunbeam (Victa 2 stroke motor) was tested by taking one blade off then run for a short time and the base just instantly cracked apart .
So besides the mower doing everything it should ,I'd prefer an alloy base that lasts but if you look after your mower most will last decades.
Yes I agree Supa-Swifts were robust ,the tri blades worked well and should be better balanced than a twin blade .
