It's also worth comparing process nodes.
The Snapdragon 8 Gen 2 is on TSMC 4nm compared to the A14 on TSMC 5nm.
Also, the Cortex X4 spec projections are based on the second gen TSMC 3nm process node that isn't in volume production yet. If the M3 is announced (as rumored) next week at WWDC on the first gen TSMC 3nm, we'll have some basis for comparison (at least as far as projected specs go).