You're investing the the community building and creative power of the team.  To answer the question, you must know the team, and how their skills and incentives synergize to create leverable value.  I don't.  I have not read the stuff.  My intuition is that Ethereum is NXT + XCP with a contract language vaguely similar to Simon P-J's 2000 paper.  The investment potential of NXT may be similar, on many levels, although PoW emission means it's probably more robust.

I think all these systems are immature, and inevitably supplanted by a successor.  I'm not sure which generation/feature-set will provide a stable platform, and I don't care to bet on a guess.  For more I would have to read the stuff.  If I'm wrong about something fundamental, I probably should read the stuff, because writing it off may have been a mistake.  Otherwise, I saved time.