The PvP Power relics lost their "absolute bestest of the bestest" role when the DG DPS relics got 47 power put onto them. As such, pretty much all of the math I've seen actually recommends using a DG use relic and a DG proc relic rather than 2 PvP Power relics. If you use the DG power use relic on CD, you get 134.5 power averaged; the EWH passive power relic only provides 120, so the advantage even then is to the use relic unless you just can't be bothered to click a button every 2 minutes.
As to the debate between the proc relic and the passive power relic, the 73 Power that you're getting provides only 17.6 Bonus damage (Force Might factored in). Including a 1.5 sec addition to the ICD to represent downtime, DG I/E proc relics provide ~35 additional damage. Unless you're averaging better than a 2.0 coefficient averaged across all of your attacks (a vast majority of attacks manage closer to 1.6-1.7 so it's not very likely), you're better off using a DPS proc relic.
As to which proc relic you want to use, yes, if you have a substantial amount of *global* armor penetration, the K/E proc relic (Kinetic for Tech classes; Energy for Force classes) is better for you than the I/E proc relic (Internal for Tech; Elemental for Force). Keep in mind only global armor penetration apples: VGs should never use a K/E proc relic because all of their ar pen is specific to certain abilities. In addition, armor debuffs (such as those provided by Gunslingers, Guardians, and Gunnery Commandos) do not count as "armor penetration"; they are a completely separate mechanic that reduces the armor that a target has, not a mechanic that allows you to ignore a relevant percentage of the target's K/E damage reduction (which is what ar pen does). As such, the only classes and specs that should use a K/E damage proc relic are Gunnery Commandos (thanks to Armor Piercing Cell providing 35% ar pen), Focus Guardians and Sentinels (thanks to Shii-Cho Mastery providing 30% ar pen), Scrapper Scoundrels (thanks to Flechette Round providing 30% ar pen), and *potentially* Combat Sentinels (Precision Slash provides 100% ar pen for 4.5 seconds every 15 seconds, which means that you could potentially be certain that toughly one-third of your procs benefit from 100% ar pen but you could just as easily avoid it completely).