Facebook and Instagram are both part of Meta Ads, so the useful question is not which platform is universally better. It is which placement and creative experience fits your customer journey.
Use the same campaign system, not separate silos
Start with the objective and let delivery learn where results come from. Then inspect placement-level performance and creative behavior.
Match creative to the placement
Vertical video, strong first-second hooks and creator-style content often fit Reels and Stories. Feed placements give you more room for detailed messaging and proof.
Measure business outcomes
Compare qualified leads, purchases and revenue, not only engagement. Keep testing creative while protecting enough budget for meaningful learning.