War Machine has more variety of ranged attacks compared to the singular laser strike the X-66 has, along with homing missiles as well. While that single blast is a lot more useful due to its higher speed, it can only be fired from the front of the jet. War Machine has superior mobility thanks to his own style of flight and his smaller size.
War Machine also has sensors that can analysis the X-66 tech, likely telling him exactly what its packing. I can see War Machine laying on some serious pain, homing missiles are probably the most annoying thing he can use against the X-66, as it'll have to deal with them and whatever attacks he may through out as well.
The biggest advantage the X-66 has is the faster laser attack, which can intercept people who are 79.57% SoL from quiet the distance away. I'd also point out that even Tomura and Star seemed unable to dodge them as well, even from around 100 meters away. So they are noticeably faster, making it hard for War Machine to dodge.
I'm also not seeing any heat resistance on War Machine's armor. I see on the profile the armor is made out of a chromed titanium-steel alloy, meaning the lasers should be hot enough to cause significant damage to the suit, even melt it in the long run. But the most prominent point is the sheer power its packing.
The combined laser of seven X-66 were able to keep a Class P character pinned in place. Even dividing this by the seven jets, the force this laser packs is still Class P and is way above War Machine's paygrade. Meaning a single hit will carry Rhodey across the sky.
A single laser blast that pushes him into to the ground is game over, as War Machine has no way of escaping a continuous blast. Although, if Rhodey becomes aware of this he'll do anything he can to avoid that outcome, all he has to do is make sure he stays above the jet so it cannot shoot him into the ground.
Another point is the superior range, the X-66's range is Kilometers vs War Machine's Hundreds of Meters.
I'll vote for the X-66, it's win conditions seem far more doable than War Machine's. The damage inflicted by the lasers will do far more than any direct hit Rhodey can land on it. War Machine's superior flight is countered by the fact the laser is much faster than him.
Due to the advance sensors that can detect/analyze bio-signatures, I doubt War Machine could lose the X-66 in the clouds or something. Being able to take pot shots at War Machine from outside of his range also doesn't hurt, although as I said this part is less of a problem due to the fact the laser can only be fired straight forward.
