For “performance” in this category—mainly noticeable energy, focus, and appetite support—Hydroxycut Hardcore has the clearer on-paper mechanism because it discloses a high caffeine dose and is repeatedly described as providing strong energy during workouts and demanding days. That said, the same stimulant intensity is also what drives many of the negative experiences (jitteriness, dizziness, anxiety, and sleep disruption).
Genius Burn’s performance appears more variable: many buyers report sustained energy, reduced cravings, and improved focus without jitters, but there are also credible reviews saying they felt little to no effect, especially considering the higher price. If you want “felt” effects fast, Hydroxycut is more likely to deliver—if you tolerate it.