It is the exact same just sized to fit 25.4mm rails. I will release the new rollers for the other 2 sizes in a day or 2.
The answer depends. What size/strength tubing can you get? The plastic is the same. In the US 25.4mm (1″) OD is usually cheaper most everywhere else 25mm OD is cheaper. If you are going stainless.
If you are just milling foam I wouldn’t spend the money. As with any changes it depends on your use. Other than testing the 25.4mm parts I doubt I will spend the money on Stainless again.