Compression ratio:
r = \left(\frac{P}{P_0}\right)^\frac{1}{1.4}
where P_0 = 14.7 psi.
Engine 1 (P = 400 psi): r = 10.59.
Engine 2 (P = 800 psi): r = 17.37.
Diesel cycle thermal efficiency:
If we assume \alpha = 2 (cut-off ratio) and \gamma= 1.4, then:
\eta_{th} = 1 - \frac{1.17}{r^{0.4}}
Engine 1: \eta_{th} = 0.544.
Engine 2: \eta_{th} = 0.626.
Engine 2 is more efficient.
Air volume per cycle (at atmospheric pressure):
[Here, I'm not sure what you mean by «5 parts air» and «1 part air»; I'm assuming you mean one engine's rpm is 5X faster than the other one or one has 5 cylinders and the other one has 1 cylinder]
V \propto ND^2S
and the energy per cycle is:
E \propto \eta_{th}V
\frac{E_1}{E_2} = \frac{\left(\eta_{th}ND^2S\right)_1}{\left(\eta_{th}ND^2S\right)_2} = \frac{0.544 \times 5 \times 10^2 \times 30}{0.626 \times 1 \times 10^2 \times 10} = 13
Engine 1 should produce 13 times more power than engine 2.