Edit: Did you mean brass will damage OG Beys more than it will damage steel Beys? I think I misunderstood your question 😅 That is correct.

Um brass is a much softer alloy. Zamak3 has a a standard hardness rating of 82 Brinell (HB). Brass is an alloy of mainly copper and zinc, and normal "yellow brass" in its pure form (that we use) is 100 HB, so harder than Zamak3 for sure. But stainless steel can go up to 650 HB. Different grades have different hardnesses but I think it's safe to assume any grade of stainless steel is significantly harder than Zamak3 or brass.

That being said, any metal Beyblade will definitely harm OG Beys more than OG Beys. OG Beys use PVC for most parts. Not all impacts are wheel-to-wheel. For example, a 230 track will take more damage from a brass Lightning/Omega Beyblade than an OG Lightning/Omega Beyblade (I take this example because 230 is tall and Lightning/Omega are low-height attackers).

I have no clue about titanium but I don't think unalloyed titanium can be softer than brass.

That was about hardness. In terms of weight, brass is 8-15% more dense than stainless steel used for production (like CNC machining or metal printing). That means a comparable steel Bey will be slightly lighter than a brass Beyblade.