The rule number 1 is mentioned by Slaw - YOU have to make the comparison - and it all depends on your TASTE and your SYSTEM.
But who said you can not use experience of other members..?
Just yesterday I did a shout-out of 5 power cables, coincidence or not - but mainly on my DAC (AN Tube dac).
While they were not Black Mambas or Pythons, the participants were: Shunyata Diamondback, Copperhead, Taipan Helix Alpha, Kimber PK14, Kimber PK10.
These all cables, exept probably Diamondback (which proved just what it had to prove for the price: just lower noise floor a bit, tigten bass, and pretty much thats it), made quite big changes to the sound.
If you want specific descriptions what changes what cable brought, please write me a message, because i will go now srtaight to the point: the clear winner for my taste was ( probably the cheapest cord in the group!) - KIMBER PK14 - its and amazing power cable to put specifically on DAC.
Strenghts: WIDE soundstage with ACCURATE/PRECISE imaging, CLEARNESS and DETAIL on everything: VOCALS, INSTRUMENTS; back instruments are no more forgotten : you can nicely follow the RYTHM. NICE STRINGS!!
Taipan Helix Alpha also was nice. With very interesting and enjoyable, sort of "hi-end taste" timbres.
I was thinking what if Taipan cost was same as Kimbers PK14.. what would I take.. I think I will still stick to Kimber - thats how good it was!