Under the skin they are not!Well as under the skin they are nearly the same car. The 200 will be better on handerling due to the size of the car. But the 400 was the best car in it's class on ride when it was launced. The MK2 200 is still and very fine car by mordern standard today. Just remeber the 400 with the L series argour under the bonnet will not be pin sharp in the bends, due to the extra weight from the diesel engine.
If you jack both the MK2 200 up on a ramp next to a MK2 400 you will be suprised at what you see. They share quite abit in common. The rear setup alone is the same. The front complete diffrent but thats Honda for you.Under the skin they are not!
MkII 200 and MkI 400 are R8s. The MkII 400 is an HHR.
You're thinking about the MkII 200 and MkI 400 being comparable.
From the size comment you're trying to compare the MkIII 200 (R3 - derived from the R8) and the MkII 400. They're completely unrelated.