I assume you are talking about the relics with proc dmg vs matrix cube.
The proc relic by far here's why:
- 30% chance to proc, but can only proc every 3 gcds (4.5secs). It can also proc from dots and offhand attacks. While ur on the target the chance for it not to proc every 4.5 seconds is less than 2%.
- The dmg gets crit bonus, crit modifier bonus and power bonus.
Figure out your 3 gcd rotation, how much does the str bonus effect dmg every attack, how much dmg increase does it give in 3 gcds, and compare this number with the proc dmg (factor in crits & modifiers) . The difference is huge.