yield strength matters when we are talking about structural materials. Titanium is better in a structural role, for example the frame of an airplane. at the same resistance of a good steel, it weights less.
However, when you want to investigate resistance to impact, yield strength is irrelevant. You are almost certainly going above that. What is important is if the material can absorb the impact energy before it breaks. This can be seen indirectly from the graph of stress and deformation: deformation energy is the area below the stress curve. However, considering that both the stress law and the elongation at breaking point are fairly different, it is not immediate. More easily, it can be seen from the given resilience value, or charpy test. That measures the energy absorbed by a standard block of metal impacted by a standard weight. From the links you posted, Titanium has a resilience of 17 Joule. Mangalloy has a typical value of above 112 J, which is an incredibly high value.
Furthermore, not only Mangalloy has an excellent ability to absorb energy: the impact turns the unstable structure of the alloy from more malleable austenite to harder ( although brittler) martensite, reaching significant hardness. This conditional and superficial phase change should mean that projectiles have an harder time penetrating and glancing should happen more frequently for normal AP rounds.
Basically, from all I read Mangalloy is the holy grail of armor, at least in our simplified context.