BiS relics sometimes has to take in acount the spec\class you are using
in a smugler class DF the BiS is the internal one, but in SS spec is the kinetic
All Gunslingers should be using the internal proc relic. The energy/kinetic proc relics require the presence of substantial amounts of global armor penetration to be valuable. Sharpshooter doesn't get any global armor penetration (it gets a single instance of specific armor penetration to Aim Shot, and not even all that much).
The class/specs that shouldn't use the relevant I/E proc relic for their power source and should instead use the relevant K/E damage proc relic are Focus Guardians/Sentinels (30% arpen from Shii-Cho Mastery), Scrapper Scoundrels (30% arpen from Flechette Round), and Gunnery Commandos (35% arpen from Armor-piercing Cell). Combat Sentinels are somewhat fuzzy as to whether they should use Energy or the Elemental proc relic: Precision Slash provides 100% arpen for 4.5 seconds every 15 seconds, which averages out to 30% arpen. However, because the ICD on the damage proc relics is 6 seconds, made slightly longer as a real CD by the need to have it proc off of attacks, it's entirely possible that you won't benefit from your arpen for those attacks. If you use Precision Slash immediately after the proc activates then you'll get the same damage as anyone else without any arpen, which makes it worse than the elemental proc relic. As such, Combat Sentinels get kinda fuzzy: the law of large numbers states that you probably get ~30% arpen applied to your proc over time, but sometimes that just doesn't apply.
Keep in mind, the differences between choosing the proper DG proc relic and the "wrong" DG proc relic (as long as you're getting a DPS relic), is single digit changes in total DPS. When you're already pushing 1.9-2k DPS, you're probably not going to notice any difference in whether you're using the correct DG relic, especially since the natural variation in your DPS thanks to lag, variations in skill and reaction speed, etc. are all going to make a *way* bigger difference.