The Vinci engine seems very very similar to the RL10B. Both are hydrolox expander-cycle engines with 465 s Isp and extendible nozzles with a ~250:1 expansion ratio. The biggest difference is that the Vinci has a bit less than double the thrust.
Why design a whole new engine rather than just buy two RL10Bs when they are so similar in role, function, and form? Conversely, why wouldn't NASA's Exploration Upper Stage use two Vincis rather than 4 incredibly expensive RL10s?