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

Seems like an unfair comparison if you have one engine already, but not the other. However, if one was planning a build, if both of these engines choices are present, and a person was on a budget, the vote would be to build the 318. You'd have to add in the cost of the 340 to the build before adding in the cost of building the 340