Titan Basicline® is completely nickel-free and is suitable for sensitive and very allergic people. It is half as heavy as steel. It is not really the titanium itself that is so good for the body but the layer of titanium oxide that forms on the surface. The oxide layer also acts as a barrier against other substances in the titanium leaking into the body. If the titanium oxide surface is worn away, a new layer is formed immediately.
Both Surgical Steel and Titanium are basically "silver colored" but are nowadays available in several different colors.
Titan Blackline® is black jewelry in Titanium, not "dyed" black in the classic sense, the black color is created through an electrolytic anodizing process, not by applying an additional coating layer, such as PVD coating. This means that the black appearance does not come from a separate metal or material coating, but from a treatment of the titanium surface itself.
Blackline® is glossy black and a delight to the eye, they are incredibly beautiful as they are but also really cool if you combine with other colors.