Well the price thing could be argued either way depending on what you use and how good of deals you can get and so could HP. If you are thinking that you want to use stock heads than the 6.1 will be faster, it will make more HP OOTB and weigh a lot less, plus with a big stoker kit in the future and CNC ported stock heads it can make incredible HP, the big block will need heavily worked Victors to keep up in the HP department. Now TQ on the other hand it will be hard for the hemi to keep up as most of the stroker kits for the hemi only get up to 440 or so cubes while the 400 block can swallow over 500 cubes. To make 700 hp with a hemi you add a 440 stroker kit and port the heads, 950hp on a mopar single plane intake or XV intake and big cam and you are there, stock blocks can take it with their cross bolted mains. 700 hp in a 400 block is scarey, you need a good girdle, aluminum caps, aftermarket heads...

You will get lots of different takes on the subject but that is my