And then t'Telnur Oklebwaira comes out of nowhere with a technology that will defeat both of you, muhahahaha! (if only xD)
The Federation would develop some tech to resist it, and the Xim would mutate themselves beyond recognition in an attempt to gain immunity. Eventually you'd just be dealing with two pissed off and invincible nations, who have finally put aside their differences and allied under a single cause: fucking up the t'Telnur.
Edit: @Hael I'm sure you'll be glad to know that i'm going to be using meters to give a rough estimate of the size of my ships xD
I'm glad to know that I have a translator on hand