Mac's built in preview tool is nice because, well, it's built in. But a few things are worth pointing out.
- Images and annotations get flattened. So you can never edit annotations later.
- No history of markups or tags or filters to organize them
- No built-in link sharing or permissions
- No other file types like PDF (although you can do with the Mac Preview tool), Google Docs/Sheets/Slides, URL, etc.
- No integrations like Slack (click any image/pdf in slack to annotate) or Google Drive (click any file in Drive to annotate)
- No image insert and multi-page Mac native does have some cool stuff tho, like a signature block (coming soon) and instant view on iPhone (which we don't have, but we do have mobile web annotation so you can go between desktop and mobile freely if you are logged in.