Today, dollar for dollar, is the 318 faster than the 340 ???

The extra stroke of a 360 makes a hella difference.
I’ve heard people that ran a 340, then switched to a comparable 360, and say they will not go back.
My observation, Your milage may vary.

Depending on gears and stall for each can make a big difference, most cars are under geared and stalled. Lots only run 3.23-3.55 which is gonna be the optimal max performance gear for less 1% for the other 99% of the other cars out there those gears are always gonna be better for larger engines.

To me that's the main reason to build larger displacement, most 360 probably should be running one full ratio lower than 3.23-3.55 and a 340 probably 1.25 lower.