Crossplane Crankshaft
Flat Plane Crankshaft
The Bottom Line
Crossplane Crankshaft Advantages: Smooth, vibration-free performance; distinctive American muscle car burble.
Crossplane Crankshaft Disadvantages: Heavier (harder to rev), requires larger crankcase.
Flat Plane Crankshaft Advantages: Lighter, more compact, more responsive (high-revving), better exhaust scavenging.
Flat Plane Crankshaft Disadvantages: Prone to vibration, lower torque levels.
Good video showing how the pistons move relative to each other:
https://www.youtube.com/watch?v=2AzrOPPZFzs
(Should have added exhaust sounds instead of music in the video.)