As for me personally "at this moment", I have 750 bucks into my "free" 318 with dual quads, summit cam, and home ported heads. I'm up to racing any bone-stock 340 with 3.23 gears and stock tranny/converter. You can't even buy a good 340 block for 750 ??
Again, this is not stating 318's are better than 340, because they are not. It's stating at the lower end of the spectrum, you go faster with the 318 than the 340.