Upper Stages for Deep Space?

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RL-10 as a thrust of 110 kN or 24.7k lbf.
The Broadsword engine from Master Space Systems burns methane and produces 25k lbf.
https://en.wikipedia.org/wiki/Masten_Space_Systems

http://www.twcnews.com/ca/antelope-valley/news/2017/04/7/masten-space-systems-wins-nasa-contract.html

Yup, it seems appropriate for a deep space upper stage.

One question I haven't been able to figure out is whether the Broadsword engine is open or closed expander cycle. Open is probably more better for higher chamber pressure and higher T/W as seems appropriate for first stages, which seems to be one of the applications for this engine. That might limit the ISP as an upper stage engine.