Honestly, relying on just one tool is a trap because their databases vary wildly. For my own sites, nothing beats Google Search Console for accurate traffic and indexing data—it's the only real source of truth.
For competitor analysis and backlinks, I use a hybrid approach. Ahrefs is still the gold standard for backlink profiling and finding toxic links, but the price is steep. For everyday checks or tighter budgets, I often use SE Ranking or Mangools, which offer about 80% of the functionality for a fraction of the cost.
For estimating competitor traffic, I cross-reference Semrush with the free SimilarWeb browser extension. SimilarWeb is surprisingly accurate for medium-to-large sites, while Semrush is better for spotting keyword-level traffic opportunities.
My recommendation: don't overspend on Ahrefs or Semrush right away unless you're running an agency. Start with a budget-friendly all-in-one like SE Ranking, and only upgrade when your projects actually demand the deeper data.