>>8928502013 Surly Moonlander.
It's Steel. Double Butted. It has some frame flex (side to side) when loaded heavily on the front and rear rack. I could fix that by using lower center of gravity racks / panniers or by not loading the front end with heavy crap.
The benefits of steel vs alloy:
- Has some "flex" to it that absorbs some bumps / vibration.
- If you ding or dent it, your frame isn't completely compromised, structurally.
- in the rare event something does brake on the frame, any shop with a welder can fix it for a beer and a $5.
- it's not heavier than alloy because it needs less material to achieve the same structural strength.
- cheaper than alloys, usually.
- wont strip out threads (if your frame has any) as easily. Ex. being the derailleur hanger mount but it's not a huge advantage.