IM Dude's breakdown is accurate — it really comes down to margin control vs risk distribution. Owning the offer means 100% margin but you're fully exposed if the product/conversion rate is weak. Affiliate means lower margin per sale but you can test multiple offers and only scale the ones that already prove themselves with real data.
One thing worth adding: the "stability" question depends heavily on whether you're optimizing for ad account longevity too. Direct/owned offers give you more control over landing pages, creative compliance, and policy risk since you're not bound by someone else's affiliate terms — but if you mess up compliance, it's your ad account and your brand at risk. With affiliate, if one offer/network gets your ad account flagged, you can pivot to a different network/vertical without rebuilding your entire business from scratch.
In practice, a lot of experienced media buyers end up running both — affiliate for testing and cash flow, owned products once they've found something that converts reliably and want to capture full margin.