I have the titanium and the stainless steel; which one is less likely to scratch?
I have a natural titanium and silver stainless steel. Titanium is softer and scratches far more easily, leaving shiny marks that stand out. However, titanium can be brushed back to normal with a $3 dish sponge. Steel is harder to scratch but the buffing out process is a little more involved and it actually results in you taking off a bit of material. In the hands of a careless person you could actually end up deforming a stainless steel case by buffing it excessively.
In short, the question is not which scratches more easily but how it looks when scratched, and how you’re likely to react to scratches.
If you’re happy to maintain your watch with regular brushing, keep the titanium.
Otherwise, keep the steel: it will wear its marks more gracefully even without intervention on your part.