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V₂O₃ and VO₂, are prototypical strongly-correlated materials that undergo a metal-insulator transition (MIT). The MIT in both materials leads to a concomitant structural phase transition and a magnetic phase transition in V₂O₃. Recent experiments [PRB 91, 205123, 2015] explored the sensitivity of the MIT to defects and demonstrated the MIT phenomenon in V₂O₃ is sensitive to the presence of defects while it is robust in VO₂. To explore the underlying mechanisms for this behavior we performed first-principles calculations to assess the role of defects on the structural, magnetic and electronic properties of V₂O₃ and VO₂. In V₂O₃ we find defects disrupt the antiferromagnetic (AFM) order in the insulating phase. We also find small polarons form through self-trapping or due to defects. We assess the impact of this phenomenon on the spin-flip energy between the metallic paramagnetic and the insulating AFM state with the goal of understanding how this impacts the MIT temperature. In VO₂, we explore the impact of defects on the vanadium dimerization in the insulating phase and the impact on the MIT.