by Raiden00
I owned both games with Runewars being a more recent purchase.I suggest go with Eclipse expansion, as it really makes a fantastic game better with better tech, more races and just a great expansion, and Eclipes goes well with bigger groups, something to consider.
I love Runewars too, good with any player count from 2 onwards, a great game out of the box, supports 4 players and very different from Eclipse. But it is fantasy setting with cards replacing dice. And i personally think no need expansion unless you want more of the same
It really depends, if you want two good games, get Runewars, if you are going to keep playing Eclipse regularly, expansion is the way!
Hope that helps!