the top short block is a B20b from a JDM stepwagon. (not available in the US)
the bottom block is a B16a from a JDM EK civic sir. notice the webbing on the B16a is more substantial. its really buildt for high RPM. the B20 doesnt have piston squirters which also limits its ability to perform at hi RPM.
you cant tell by these pics but the B20 cylinder walls are thicker than the B16as if you measure them but they are "thinner" relative to the size of the piston and stroke.

This B20 will be rebuilt and put into my 92 JDM Civic Sir II. i love the B16a but I need more torque which is real world street power. The B16a just doesnt have much torque because of its short stroke.

hope this helps