Attribution model choice depends on your conversion volume and sales cycle length. Data-driven attribution in Google Analytics 4 is the gold standard when you have sufficient data because it uses machine learning to assign credit based on actual conversion paths. Google typically needs 400+ conversions per 30-day period for the model to work reliably. Below that threshold, the model becomes unstable and you're better off with rule-based options. For most Canadian SMBs running multi-channel campaigns, linear attribution gives a balanced view by crediting every touchpoint equally. It's honest about the messy reality that customers interact with your brand multiple times before converting. Time-decay works better when you have a short sales cycle (under 14 days) because it gives more weight to recent interactions, which makes sense for transactional or impulse-driven conversions. Avoid last-click unless you're only optimizing direct-response channels in isolation. It systematically undervalues awareness and consideration touchpoints, which leads to killing campaigns that actually drive pipeline. First-click only makes sense if you're strictly measuring top-of-funnel awareness and have a very long sales cycle where initial discovery matters more than nurture. For clients in Ottawa's B2B and professional services space, we typically see 30-90 day consideration windows. In those cases, position-based (40% first, 40% last, 20% middle) often reflects reality better than pure linear because the discovery moment and the final conversion trigger genuinely matter more than mid-funnel touches. The practical approach: run parallel attribution models in GA4 for 60-90 days. Compare how each model credits your channels. If they're wildly different, your customer journey is complex and you need data-driven or position-based. If they're similar, your path to conversion is straightforward and linear works fine. Most importantly, pick one model and stick with it for at least a quarter so you're comparing apples to apples when evaluating channel performance month over month.