[Dark Skies]

I have never owned an alum frame but have been told that the reason the alum frames are bigger tubes is to achieve comparable stiffness with steel.

I have always riden steel frames.

Can't argue the technology since I haven't riden alum or titanium.

[Scutter]

I have never owned an alum frame but have been told that the reason the alum frames are bigger tubes is to achieve comparable stiffness with steel.

You are 100% correct, and I am wrong. Apparently I was the victim of a popular myth. Details here.