From what I remember reading, the Vasudans are a race of philosophers, not warriors. The whole combat thing never really came easily to them, and as such it makes more sense that Terran weapon systems would've been more advanced. However, the Vasudans did produce the Typhon, which when given FS2 era weapons is inferior, but stick to FS1 weapons and it was indeed the one thing on the battlefield captains absolutely did not want to see. It was dangerous as frak, and damnably hard to catch and destroy. Hence, I believe stalemate and eventual cease-fire is the most likely outcome.
Also coming to think about it, if the Shivans never popped up, I don't think beam weapons would've been created... It's always looked to me as if some GTVA weapons engineers looked at old holovids of the Lucifer pwning the crap out of planets and everything with its big-ass flux cannons and went "OMGZ WE SHUD TRY DAT!!!!" A few days of drunken engineering later and the first beam cannon manages to cut a grape in half.