This is for Elorran, didn't wan't to quote the whole post:
Those are good points, but once again, you are forgetting one thing. You said that:
"And another point, due to the nature of 'no shields' the kushan have, their ships are made far more solidly built and thus have significanly more armour and integrity"
And:
"And lets be honest, no meson bomb can compare to the power of the siege cannon. "
As I said earlier, you really can't tell how powerful the Kushans and Shivans weapons are when compared to each other, as the ships also may have different kind of armour. So in other words, even if a scout can take a short hit from an ion beam, and a sathanas can take minutes of pounding from BFRed:s, it doesn't mean that the other universe's weapons have the same effect.
Now, as I also said earlier, there is one single way of comparing weapons(and at the same time, armour) strenghts of HW and FS ships, asteroids. In FS2, a couple of hits from a fighter weapon take out any asteroid, and capships can take dozens, if not hundreds of impacts from large asteroids. Now think about asteroids in HW, in that mission of original homeworld, 3 destroyers and numerous smaller ships had to shoot for a few second to take down a small asteroid, not to mention the larger ones.
About the Siege cannon vs Meson Bomb:
This is a bit science crap, but in FS2, meson bombs create a whole lot more damage that antimatter warheads. HW:CAT manual(if I remember correctly) says that the siege cannon fires a bolt of high-energy plasma. Sure, this is deadly, and would certainly heavily damage any ship, but it's not even comparable to what an antimatter warhead would do, not to mention the meson bomb.
So to put it the same way as you: THE SHIVANS WOULD WIPE THE FLOOR WITH THE KUSHANS!!! READ IT AND WEEP!!!!