Acceleration also is in the M5's favor but it is fairly close with the manual trans. The manual CTS-V runs a email@example.com and the manual M5 runs a firstname.lastname@example.org. Close, but the M5 has the edge. What is interesting is that the DCT version of the M5 (which we are very glad Road and Track included the numbers for) beats both significantly running an email@example.com. The dual clutch transmission gives the M5 three miles per hour of trap speed and 4/10's in the 1/4 mile. Those wanting the absolute fastest acceleration will want to get the dual clutch transmission.
Both of these cars are great options. The CTS-V's considerably lower price point is very appealing considering it does not give up too much for the M5 and having been out longer it will be far easier to wheel and deal on a new purchase making the disparity even greater. Those buying used will find an even greater value. This is the CTS-V's strong point. That, and easy upgrades for more power to the supercharged LSA V8.
Road and Track says the M5 is not what it used to be as it is longer and heavier. The M5 is heavier than the CTS-V although they are fairly comparable in this regard (50 pound difference). If the M5 was lighter it would be a much better performer. For its size and weight though, it does an incredible job. The limits are high but unfortunately the communication isn't there. Road and Track complains there is a degree of isolation. So although the performance is better than previos generations as it should be, the driver communication and interaction is not. Is it really a better car because it marginally improves the performance numbers over the previous generation namely when using the dual clutch gearbox?
That is up to you to decide.