What's the most effective tag management system for deploying conversion tags quickly across multiple client properties?

For deploying conversion tags quickly across multiple client properties, the most effective general-purpose choice is usually Google Tag Manager (GTM).

Why GTM is often the best fit

• Fast deployment: Add one container snippet to each site, then manage tags centrally.
• Flexible: Supports many ad platforms, analytics tools, pixels, and custom HTML/JS tags.
• Version control: Publish changes safely and roll back if needed.
• Built for multi-site management: You can standardize setups across many client properties.
• User permissions: Good for agencies and teams with different access levels.
• Triggering and variables: Powerful enough for most conversion tracking use cases without developer help every time.

When another system may be better

• Tealium IQ: Better for large enterprises needing more advanced governance, data layering, and cross-channel orchestration.
• Adobe Launch (Tags): Best if the client already uses Adobe Experience Cloud.
• Segment / RudderStack: Better if you want more of a customer data pipeline than a pure tag manager.

Bottom line

If your goal is rapid, scalable conversion tag deployment across many client sites, Google Tag Manager is usually the most practical and widely adopted option.

If you want, I can also compare GTM vs Tealium vs Adobe Launch for agency workflows.