Where would you put better power cable?

Although there are general rules of thumb and guidelines remember the following:
All of our audio rigs are individual and system dependent. What works well for one audiophile will not necessarily work in your system and/or in a different geographic location.
Personally, I've been surprised by trying different power cords on different equipment and evaluating the sound. What I thought would be a for sure thing actually sounded better on a different piece of equipment.
Moral of the story, if auditions are free try it, and it doesn't hurt to experiment :-)
"Good Things In Life Take A Long Time"

I find that DAC makes a larger difference in my system than transport. My transport has a Shunyata Diamondback and my DAC has a Shunyata Copperhead.

Currently I have my pricier cable on my dac being a thicker gauge with better connectors.

I doubt that gauge and connector quality would be responsible for any differences that may be perceived between power cords used with a transport and a DAC, assuming (as appears to be the case here) that both cords are of reasonable quality in those respects.

Shielding and noise rejection figure to be the characteristics most likely to make a difference in this kind of application. However, which of the two components would be more critical in those respects is dependent on the specific characteristics of the noise on the incoming AC, on the sensitivity of each of the two components to that noise, on the characteristics of the noise each of the components may feed back into its power cord, on the sensitivity of the other components in the system to that noise, on the susceptibility of the two components to ground loop issues, on the proximity of each power cord to other cables and power cords, etc. In other words it's all essentially unpredictable, IMO, as several of the others have indicated.

Also, I would by no means make a general assumption that higher price correlates with better shielding and better noise rejection, or with any other characteristic that may make a difference. Although based on their descriptions it appears to me that the higher priced of your two particular cords probably does happen to provide superior shielding and noise rejection.

Regards,
-- Al

Al, Your second paragraph is particularly and succinctly well put into a liking as audio poetry and fully spelled out.
The only downside is that it ended the need for any further cable matching questions on this site. Thank God:)

Thanks, Iso. Poetry, and related to that alliteration, have never particularly been my bag. I do, however, generally try to avoid being a nihilistic nabob of negativity. :-)

Best regards,
-- Al